dapple gray copper harbor

Introduction
Geology
Brockway Mountain Views
Copper Harbor
A Gateway to Isle Royale
Copper Harbor Lighthouse
La Roche Verte
Horseshoe Harbor Stromatolites
Dan's Point
Fort Wilkins
Hays Mine (Pittsburgh & Boston)
Porter Island
Hunter's Point
Lake Shore Traps
Copper Harbor Conglomerate
Clark Mine
Clark Mine Swamp Adit
Manganese Mine
From the Keweenaw County beaches

Introduction

This article is about rocks and minerals but it is also about a remarkable place, the Keweenaw. The article includes history, relics, specimens and stunning scenery, but most importantly, it will try to explain why some people are smitten by its interesting natural appeal and beauty.

I first saw the Keweenaw Peninsula in 1950. We were on a family camping trip to see the entire Upper Peninsula of Michigan with a little fishing on the side. I was 13 years old and had great expectations of what the far north would look like. We crossed the Straits of Mackinac on the car ferry. Soon I was disappointed. The Upper Peninsula looked just like the Lower Peninsula. When we finally started north on highway 41 above Houghton I thought, this is it, just what I was looking for. I became one of the smitten.

When you brose through this article you may notice this in bold, "A Story". That means that the writing that follows is loosely connected to rocks and minerals. The stories are more like a journal that documents 70 years of collecting on the Keweenaw Peninsula of Michigan.

Geology

This is a partial photo of the USGS Geologic map of the Keweenaw Peninsula and the adjacent area. It provides abundant information about the geology of the Keweenaw Peninsula. The Lake Shore Traps are defined by a dark orange/brown band that passes directly through Copper Harbor. The lighter orange that surrounds it is the Copper Harbor Conglomerate. The contact between the Copper Harbor Conglomerate and the Portage Lake Volcanics passes through the north shore of Lake Manganese and follows the crest of the hills all of the way to Keweenaw Point. The Manganese Mine is located very close to the contact but in the Portage Lake Volcanics. The Clark Mine is about ¾ mile south of the Manganese Mine further into the Portage Lake Volcanics. The dotted lines depict additional unmapped flows of the Lake Shore Traps located under Lake Superior.

Exploration and mining in the Keweenaw Peninsula started in the 1840's. Over the years extensive core drilling was done in the search for copper resulting in a huge reservoir of professional papers defining the geology of the area. The references below provide a good summary.

Bornhorst T. J., Rose W. I., (1994) Self-guided geological field trip to the Keweenaw Peninsula, Michigan.

Bornhorst T.J. Barron R. J. (2013) Geologic Overview of the Keweenaw Peninsula, Michigan, Institute on Lake Superior Geology.

Cannon, W.F., and Nicholson, S.W. (2001) Geologic map of the Keweenaw Peninsula and adjacent area, Michigan, U.S. Geological Survey.

Brockway Mountain Views

Copper Harbor

Copper Harbor is a pleasant little village that is the destination of many summer tourist and mineral collectors. In the 1840's it was a working outpost with Great Lakes schooners moored in the harbor unloading miners and supplies. It was the gateway through which a vast copper mining legacy was established on the Keweenaw Peninsula.

Lighthouse Point

The Copper Harbor Lighthouse is just barely visible in this photo on the distant arm of land to the right of the pine tree that covers the entrance to the harbor.

Horseshoe Harbor

Horseshoe Harbor with its deposits of fossil stromatolites is several miles up the coast from Copper Harbor about where the right margin of the photo intersects the horizon.

Lake Shore Traps

The basalt flows of the Lake Shore Traps pass right through the harbor. There are outcrops just south of the lighthouse, along the shore in town and on Porter Island and Hunters Point. They then turn inland west of the Copper Harbor Marina.

Inland from Copper Harbor, just above center, is Lake Fanny Hooe. It is about 1 mile long and 1/4 mile wide creating a narrow strip of land between the lake and the harbor. The high range of hills on the horizon is the upturned edge of the Copper Harbor Conglomerate.

Fort Wilkins

Reports of copper from Dr. Douglass Houghton's 1840 geological survey of the south shore of Lake Superior caused a "rush" of prospectors and miners to the area. In 1844 a fort was built on the narrow strip of land between Lake Fanny Hooe and Lake Superior to maintain law and order.

Clark Mine

The Clark Mine is located just over the ridge at the upper right corner of the photo.

Manganese Mine

The Manganese Mine is also located just over the ridge at the upper right corner of the photo about ¾ of a mile north and a little west of the Clark Mine.

Copper Harbor Conglomerate

This photo was taken from the top of Brockway Mountain. By definition Brockway Mountain is a "bald mountain" meaning even though the peak is not high enough to be above the "timberline" it is devoid of trees. The reason for this is not clearly understood but it must be the result of unique environmental conditions.

The cliff is one of the largest exposures of Copper Harbor Conglomerate on the peninsula. The hillsides in the distance are also tree covered slabs of conglomerate. More detail about the Copper Harbor Conglomerate will follow.

This view is looking west from the top of Brockway Mountain. In the distance about 6.3 "straight line" miles is another high point on the crest called Lookout Mountain. It also has the "bald mountain" environment with exposures of Copper Harbor Conglomerate but is rarely mentioned in geological papers.

The pine tree just to the right of center points to the location of Agate Harbor. If you enlarge the photo you will see a notch in the coastline that defines the Harbor. In 1840 Charles W. Penny accompanied Douglas Houghton on his geological survey of the Keweenaw Peninsula. Penny reported in his journal that he worked a long time trying to extract a large red agate out of the basalt at Agate Harbor but had to leave it to move further down the peninsula.

Reference: North to Lake Superior, The Journal of Charles W. Penny, 1840.

Copper Harbor

1. At the dock is the Isle Royal Queen II that transported tourist to Isle Royal from 1960 to 1989.

2. The white tower with a red roof is the old pilot house of the freighter Altadoc that was driven aground on Keweenaw Point in 1927. The pilot house was salvaged and used as a two room hotel and restaurant until it burned down in the 1980's.

3. The building with the gambrel roof is the Isle Royal Inn. Good food in the old days.

A Story……I can't remember exactly when the Harbor Haus Restaurant was built in Copper Harbor. But it was a big deal. Fine dining came to this little town that catered to rockhounds, mineral collectors, snow mobilers, mountain bikers and bird watchers. It was founded by Maiken and Fritz Ehlers from Delitzch, Germany. Fritz caught on to the mineral heritage of Copper Harbor and had the large float copper moved to the entrance of the building. There is a four-sided fire place in the middle of the dining room that has a few interesting mineral specimens on mantle.

Maiken and the college girl wait staff would be dressed in German costumes. When the Isle Royale Queen returned during the evening meal they would line up outside, lock arms and do a Ziegfeld Girls kick dance. The people on the Queen would be lined up on the deck waving vigorously. The bell in front of the Harbor Haus would ring and the ships horn would answer back.

A Story…..I recall going into the Keweenaw Agate Shop and the professor showed me an agate that he just acquired from a tourist. It was a "knockout"! It was almost perfectly round, about 6.0 cm in diameter, with concentric bands alternating in brown and bright yellow. It was the yellow bands that made it so unusual. I couldn't talk him into selling it. I think he was planning on keeping it.

The two specimens below were purchased from the Keweenaw Agate Shop. There was a third one that I failed to photograph. It was a very nice copper crystal group, flat with end to end crystals. Years ago there used to be a "swap" in South Gate, Michigan where local collectors would sell and swap specimens. I offered the copper crystal specimen on my table. A young couple looked at it from every angle, went into a huddle and came back and purchased the specimen. Many of you know them; it was Marc and Debra Wilson. Marc was beginning his career in mineralogy including many years at the Carnegie Institute and Debra became an expert in mineral photography.

A Gateway to Isle Royale

Isle Royale is an extremely interesting place. People want to go there. It is a pristine wilderness that tends to draw adventurers. The geology is the mirror image of the Keweenaw Peninsula. It is the northern upturned edge of the of the Keweenawan geological formations that correlate with the southern upturned edge exposed on the Keweenaw Peninsula. Geologists have done a lot of work there. The island is pockmarked with prehistoric diggings that are studied by archeologists. Over the years tourists have flocked there. The tiny village of Copper Harbor has provided access to the island for the last 90 years.

The Water Lily was the first boat to carry passengers to Isle Royale on a reasonably regular schedule. In 1930, Charlie Kauppi a commercial fisherman from the village of Gay on the shore of Keweenaw Bay, moved his fishing boat up to Copper Harbor to start a business. It was a wooden hulled boat with an enclosed deck, great for seaworthiness but only a few portals for sightseeing. It also did not have the safety features preferred by the coast guard. After a few years Kauppi replaced the Water Lily with the 48-foot Copper Queen also with a wooden hull but with more of a yacht-like style. In 1938 he introduced the 40 foot Isle Royal Queen complete with all of the required safety features certified by the coast guard.

In 1955 Captain Kauppi sold the Isle Royale Queen to Ward Grosnick. In 1960 the Grosnick family introduced a new larger boat with more power reducing the travel time from 6 ½ hours to 4 ½ hours. The new boat was named the Isle Royale Queen II and remained in service until 1989.

In 1971 The Donald Kilpela family became the new owners of the Isle Royale Queen II. The business continued to expand and in 1989 the boat was lengthened by 24 feet increasing the passenger capacity from 57 to 100, and re-christened Isle Royale Queen III.
In 2004 the family started looking for a new improved boat. Surprisingly they found exactly what they wanted in Cape Canaveral, Florida. It was named "American Freedom". A purchase was made and they sailed around Florida into the Gulf of Mexico then up the Mississippi River. They then entered the Illinois River and made their way to Chicago, then through Lake Michigan and Lake Superior to the dock at Copper Harbor. This large comfortable ship was renamed Isle Royale Queen IV. It reduced the travel time to about 3 hours and remains in service today.

Below...is an old collection of Isle Royale beach pebbles that were on display in a building in Copper Harbor. I first saw this collection in the late 1950's but it was there throughout the 60's and into the seventies. It dates back to a time prior to National Park restrictions. The collection was displayed on several large picture frames and included greenstone, agate, prehnite and other microcrystalline quartz. It was photographed in 1974. Sometime after that, the building changed hands and I don't know what became of the collection.

This huge datolite nodule is considered by many to be the finest in the world. It was found by divers along the shoreline of Isle Royale during a 16 year period when collecting under water was legal. In a court case it was found that the National Park Service did not have jurisdiction of the land at the bottom of Lake Superior. Starting in 1981 many pounds of datolite nodules were collected. In 1997 the National Park Service was granted control of the lake bottom out to a 4.5 mile boundary and the collecting stopped.

This interesting 16 year period is documented in detail in Tom Rosemeyer's article "The Occurrence of Porcelaneous Datolite in Michigan's Lake Superior Copper District", Rocks and Minerals Magazine, May June 2003.

A Story…..In 1981 or 1982 we made a trip to Copper Harbor. I had not heard about the datolite bonanza but ,as usual, I wanted to see what Rich Whiteman and Ken Flood had for sale and catch up on the collecting news. I found out that they had a new building down in Dollar Bay. When I walked in there was a large 12 foot table covered with datolite nodules from Isle Royale. Some were very large and all were chalky white caused by the alteration of the outer skin due to long submergence in water. In my excitement I forgot that I had a camera in the car. It would have been great if I could have shown all of you that view.

Copper Harbor Lighthouse

A Story…..In 1950 on our first family camping trip to Copper Harbor you could drive your car out to the lighthouse. I was 13 years old and I was hounding my dad to stop at an agate shop but he was bent on going fishing. On the road to the lighthouse there was a two track that branched to the right (east) a short drive led to Lily Lake. While my dad was getting out his fishing tackle I noticed a raft that the local town kids had built. It was four untrimmed logs loosely bound with rope. It had an odd shaped piece of plywood for a deck and a long pole was leaning on a tree. I launch the raft and had a Huckleberry Finn moment. When I got back my dad had two large Northern Pike on the stringer. My dad did eventually stop at an agate shop and I became a collector of rocks and minerals.

In 1995 Virginia and I moved north to the "Tip of the Mitt" of the Lower Peninsula of Michigan. We were 250 miles closer to the Keweenaw. While talking to some of our new neighbors, Lorain said that she was born in Copper Harbor. That got my attention! She was about my age so she was born there in the late 1930's. She told me that her father was a miner and she attended the one-room schoolhouse in Copper Harbor. She also described an interesting tradition among some of the miners. She said that every New Year's her father would pour some molten copper into a bucket of water. He would sit down at the table with her and ponder over the shape of the copper. He would then tell her fortune. It would always be something wonderful, like she would marry a prince and live a life of great riches.

La Roche Verte

When Douglas Houghton, Michigan's first state geologist, planed his expedition to Michigan's Keweenaw Peninsula in 1840, he invited a good friend, Charles W. Penny, to join him on the trip. While Houghton was absorbed with collecting geological specimens, Penny was writing a daily journal recording their experiences. The book "North to Lake Superior" is a publication of the journal.

Penny traveled in a Mackinaw Boat northward from the Sault with C. Douglass, B. Hubbard and F Hubbard. The boat contained 13 barrels of supplies, tents and luggage, four French Canadian Voyageurs manned the oars. Houghton was to follow later in another boat.

As they traveled the Lake Superior shoreline, Penny describes daily events such as storms, difficulty in finding a place to camp and how good white fish tasted after a long diet of lake trout. He describes in detail the large green vein, La Roche Verte, that protruded five feet above the water at Lighthouse Point, Copper Harbor. He also mentioned that Houghton blasted the vein down to water level while assessing its value in copper. He describes working for some time trying to chip a large red agate out of very hard basalt at Agate Harbor and having to leave it to continue the trip.

There is an interesting story of how the 1840 journal written by Charles W. Penny came to be published. On the cover of the book it states that the foreword was written by John D. Voelker. Voelker was a Michigan Supreme Court Justice in Marquette County. He was also an author and, under the pen name Robert Traver; he wrote some well-known novels. As a result of his writing he received mail from his readers.

One letter came from Gregory Harrier of Berkley, California explaining he had an old journal written by his grandfather in 1840 while accompanying Douglas Houghton on a geological survey of Michigan's Upper Peninsula and would Voelker like to read it. Of course Voelker replied "yes" and he received the faded yellowed document. Gregory Harrier offered the journal to Voelker who then delivered it to the Marquette County Historical Society where it was copyrighted and published in 1970.
There is an entry in the Charles W. Penny Journal on Friday, July 3, 1840 that describes his view of the famous green vein at Lighthouse Point. Here is a quote:

"It appears above the ground, at the first mentioned point only two or three rods, and then it is covered with the forest; but from the shape of the ground I should think that it runs near the surface. It contains pure malachite, green oxide, and copper black. The vein is composed of calioruous spar and these kinds of ore are disseminated through it. Some of the specimens are very rich while others contain but little metal. Our favorable symptom is, that no native copper has been found in or near the vein."

The suggestion that the green color of the vein was due to malachite is suspect. Penny was suffering from boils when this was written and did not have an opportunity to converse with Dr. Houghton. Later in 1844 when the Pittsburgh and Boston Copper Harbor Mining Company sunk an exploratory shaft on the vein just behind where the lighthouse is now located, the vein was described as green copper silicate, an obvious reference to chrysocolla. In fact the specimen from this vein at the Seaman Museum is bright blue chrysocolla with shades of green and I remember as a kid on a family vacation in 1950, I picked up a small fragment of bright blue rock at the vein.

Horseshoe Harbor Stromatolites

Stromatolites are the fossil remains of a very old primitive lifeform. The reference given below describes them as "laminated cryptalgal carbonates". Some professional papers describe the lifeform as slimy sticky cyanobacteria. The sticky material binds together particles of sediment creating felt-like living matts. Upon burial the matts have a propensity to crystallize as carbonates, calcite or aragonite. If you research the term "stromatolites" you will certainly see a photo of modern stromatolites in Shark Bay, Western Australia showing matts draped over hummocks. Here is a reference that specifically describes the geology at Horseshoe Harbor and Dan's Point:

Elmore R. D. (1983) Precambrian non-marine stromatolites in alluvial fan deposits, the Copper Harbor Conglomerate,
Upper Michigan, Department of Geological Sciences, The University of Michigan,

To get to Horseshoe Harbor you drive to the end of the pavement east of Copper Harbor. You continue to drive east on a gravel road one mile uphill to a two track on the left. Drive north on the two track until you see a sign "Trail to Horseshoe Harbor". It is about a ¼ mile hike to the Harbor. On the trail you may notice a line of wave sorted gravel winding through the woods defining a shore line when the water level in Lake Superior was higher than it is today. Horseshoe Harbor is in a conservancy, no collecting.

Dan's Point

Fort Wilkins

The region was a wilderness and in the interest of maintaining order, William Wilkins, United States Secretary of War, dispatched companies A and B of the 5th regiment to Copper Harbor. They arrived on May 27, 1844 and immediately started to clear land for a fort.

The buildings of the fort were surrounded by a wooden palisade on three sides. The south side faced Lake Fanny Hooe. Remnants were still standing when the fort was restored its current condition.

Above…..In 1965 while camping in Fort Wilkins State park just east of Copper Harbor, we ran into these divers that were exploring the depths of Lake Fanny Hooe. They were looking for the fort's cannons. Supposedly the cannons were pushed into the lake when the fort was abandoned in1870. The cannons were not found but various other items were recovered.

One of the most interesting finds was the long cross-cut saw. The great length was required to cut the huge virgin white pines that covered much of Northern Michigan. A cross-cut saw has two handles one at each end. On this saw the handle on the right is missing, this and the fact that it was found on the bottom of Lake Fanny Hooe strongly suggests that the saw was used for cutting blocks of ice to preserve food during the summer. Blocks of ice were often cut in the winter, placed in a well shaded shed and covered with a mound of saw dust. In that manner the ice would last all summer.

They also found a water-logged dugout canoe that is on display in one of the buildings.

Miners Hat…..This is a miner's helmet made from hog's hair and rosin displayed in one of the buildings. I could not find a reference for using hogs hair in this manner but very similar helmets made from felt and rosin were used in Cornwall, England. A candle would be attached to the helmet held in place with a blob of clay.

Ontonagon Boulder…..The famous boulder spent some time at Copper Harbor. In 1843 it was in the hold of the schooner Algonquin moored in the harbor while being transported to Detroit by Julius Eldred. Due to legal ramifications caused by the fact that the boulder was removed from Indian lands, Eldred was informed that the United States Government was taking possession of the boulder. It was agreed that Eldred would transport the boulder to Detroit and deliver it to the care of George C. Bates, the United States District Attorney. Later, Eldred was awarded $5,664.98 by Congress for his expenses.

"Eldred and Co. Dealers in Hardware and Leather"…..This old plank from a shipping crate provides evidence that in 1843 Eldred was in Copper Harbor with the boulder.

Hays Mine (Pittsburgh & Boston)

"The Hays Mine, located at Fort Wilkins State Park (there are also pits on Hays Point), was started in 1844 after soldiers building the Fort ran across large rocks that contained a black copper oxide. Miners from the Hays Point operations were sent to explore the area and discovered the continuation of the black copper oxide veins discovered at Hays Point. In 1845, two shafts were drilled and yielded about 40 tons of ore. Later in the year a third shaft was sunk down to a depth of 120 feet. Exploration work tracked the vein across the lake and an adit was drilled into the side of the hill. During this time, the mine owner (The Pittsburg and Boston Company) began work on another mine south on the Peninsula that would become the first profitable copper mine on the Keweenaw, the Cliff Mine. All three shafts can be seen today; however, because they are on State Park property, no collecting is allowed."

The above is a quote from the Mindat location page description, Paul Brandes.

Note: Hays Point is the same as Lighthouse Point.

A Story…..One day at the Seaman Museum I asked George Robinson if I could photograph the tenorite cobbles that were found during the construction of Fort Wilkins in 1844. He very kindly went into the storage room and came back with a cart and four of the large black cobbles. I hesitated, thinking that I should not handle the museum specimens. It became apparent that George was not going to place them on the table for the photography. I started to pick up one of the cobbles with one hand, feeling the heft, I quickly used both hands to move the cobble. I looked at George and he was grinning at me. He had just taught a lesson in specific gravity without saying a word.

Many years ago there was a small article and photo in one of the rockbound magazines showing a very desirable banded tenorite specimen. It was found on the beach at McLain State Park forty miles southwest of Copper Harbor. The point is that if you find a black rock on the beach that is significantly heavier than it should be take another look.

Fanny Hooe Creek is only about 1000 feet long. It carries the overflow from Lake Fanny Hooe to Lake Superior as it runs parallel to the west palisade of Fort Wilkins. One day I walked on the rocky creek bed over to the west bank near the park ranger residence. At the water's edge I found this datolite nodule. This was a strange place to find datolite. I looked closer, near to where the datolite was found there were two large chunks of Kona Dolomite. There is no Kona Dolomite in the vicinity of Copper Harbor. It comes from near Marquette. This was a discard pile. Someone had dumped a nice datolite specimen.

Porter Island

This is the full view of Porters Island which is about ½ mile long. It is positioned as a barrier island that protects much of Copper Harbor from storm waves. At the right end of the island (east) is the deep water channel that allows passage of boats into the harbor. At the left end of the island (west) is a small opening between Porters Island and Hunter's Point that is shallow and filled with rocks of the Lake Shore Traps.

In 1843 a "Government House" was built on Porters Island. It was a land office that issued mining permits and the island takes its name from Joseph Porter the land commissioner. Later a hotel was constructed next to the Government House.

Reference: Monette C. J. (1976), The History of Copper Harbor, Michigan.

This photo shows the western end of Porter's Island on the right and the eastern end of Hunter's Point on the left. The rocks in the water between the island and the point are part of the Lake Shore Traps that extend along the outer shore of Porter's Island and along Hunter's Point. The 1843 "Government House" was located just to the right of the white pine tree on the island.

A Story…..In later years Virginia and I started staying at motels in Copper Harbor rather than camping. After many years of beachcombing throughout Keweenaw County it dawned on me that I had never been on Porter's Island. There was a canoe on the grass at the motel and I asked the proprietor if I could use it. She gave me a paddle and I got my bag of hammers and chisels and started for the island. It was a day just like you see in the photo above. I pulled the canoe up onto the beach to the right of the white pine tree.

As I was picking up my tools I heard a strange hissing sound. I noticed that the trees on top of Brockway Mountain were trashing back and forth. Within minutes the harbor was covered in whitecaps and rollers were breaking on the rocks. I tried to paddle the short distance to get in the lea of Hunter's Point but was blown back twice. Finally I cut a long pole using my hammer and chisel enabling me to push over to Hunter's Point. From there it was shallow water all of the way back to the motel. Lake Superior can be dangerous. The water is very cold and hypothermia is a concern. Eventually I was able to get to Porter's Island. During a period of low water levels people were able to walk over the rocks to the island.

Hunter's Point

The trail to Hunter's Point starts at the Copper Harbor Marina. As you drive into the marina there is a large parking area. To the left (west) at the water's edge is the trail head. In the old days we were able to extract agates from the Traps exposed at the tip of Hunter's Point. The entire point is now a Copper Harbor municipal park and collecting is not allowed.

Below…..are specimens collected at Hunter's Point prior to the establishment of the Copper Harbor Municipal Park.

Lake Shore Traps

The Copper Harbor Formation is composed of Copper Harbor Conglomerate that is interfingured with 31 basaltic flows that have been named the Lake Shore Traps. "The rocks range from Fe-rich olivine tholeiitic basalt at the base to Ferich olivine-bearing tholeiitic basaltic andesites to tholeiitic andesites." The Traps are dated to be about 1087.2 million years old. The Copper Harbor Conglomerate and the Lake Shore Traps overlie the Portage Lake Volcanics.

Native metals such as copper and silver are extremely rare in the Copper Harbor Formation. Offshore in Lake Superior there are two locations where crystalline copper specimens were obtained by collectors, Gull Rock and the Laker Pocket.

Agates are abundant in the Lake Shore Traps however, the flows are covered with forest and finding agates requires a significant investment of time.

Reference: Bornhorst T.J. Barron R. J. (2013) Geologic Overview of the Keweenaw Peninsula, Michigan, Institute on Lake Superior Geology.

1. This is a cut slab of a vein agate found in the Lake Shore Traps west of Copper Harbor. It displays some interesting mineralogy. Professional papers date these agates at around 1.1 billion years old. This specimen shows a narrow intrusion of clastic sediment about 3.0 mm thick near the bottom, brown in color. Above the clastic vein is a row of small calcite crystals that have been replaced by chalcedony. Through the center is a vein of colorful chalcedony with some banding that is about 1.7 cm thick that contains many healed fractures. It is curious to note that that the material above and below this part of the vein is not fractured. It also appears that solutions entered from left to right producing a dark olive green coloration.

2. This amygdule is filled with a fibrous Laumontite. The dark green/black coating is a chlorite group mineral probably Chamosite. George Robinson analyzed this type of coating on several specimens and it was found to be Chamosite. The diamond shapes are the contact surfaces where Calcite crystals grew on the surface of the vesicle. Based on other specimens that I have cut the Calcite crystals that protrude into the cavity are probably outlined by the green/black chlorite. The crystals are pseudomorphs of Laumontite after Calcite.

3. Agates of this type are sometimes referred to as Tube Agates due to the obvious round structures that pass through the chalcedony.

Above…..This specimen is unique in that it is an aggregate of amygdules in altered basalt surrounded with a "skin" that allowed it to be separated from the host basalt. The host basalt is also altered and has the same color and texture as the basalt in the aggregate.

Below…..The photo on the left shows the unaltered texture of olivine basalt and the photo on the right shows the altered texture of olivine basalt. This basalt was "saturated" with iron oxides but the olivine crystals do not appear to be affected.

Note…..The photos above attempted to show as much detail of the zeolites as possible. The photos below were lightened to better show the color of the olivine crystals.

"The Game Trail"…..To facilitate conversation between my son and I, we dubbed this location "The Game Trail". One of the easiest ways to hike into the wilderness over the Traps was to follow this trail through windfalls and thick brush. One day we saw a bear track at the edge of a small stream, on another day there was a pile of wolf scat and deer tracks. We used this trail for several years and finally Ken spotted a fragment of banded agate that was kicked up near a deer track.

Ken started probing in the grass in a small open area. There were no basalt outcrops in sight so I leaned on a tree thinking that it wouldn't be long before he tires of this and we will resume our hike. Within two minutes he was pulling out chunks of a large agate. It was 90 % macro quartz with a thin agate rim around the outside. It was loose in the dirt just below the grass roots. We were able to obtain a nice selection of specimens by probing in the grass. We were able to tell by the sound when the probe hit quartz. None of this material was of gem quality. The microcrystalline quartz was opaque and fractured but it displayed mineralogical features that I had never seen before in the Keweenaw. We back filled the area and I doubt that we could find the location again. Over a great many years it is surprising how many agates we found loose in the dirt.

Above right…..This agate formed adjacent to a clastic dyke. The dyke is seen here as a brownish red mudstone mixed with sub angular particles of rhyolitic basalt. The rhyolite particles come from the weathering of the rhyolitic pebbles and cobbles that are abundant in the Copper Harbor Conglomerate. The highlands that produced these alluvial pebbles and cobbles have eroded away and the basalts that are currently observed on the Keweenaw Peninsula are iron rich mafic basalts.

The mafic basalt that hosted this agate and clastic dyke is described in professional papers as Fe-rich olivine tholeiitic basalt and can be seen here at the lower center of the specimen.

The sediments in the clastic dyke show some stratification and significant alteration. Porous areas have filled with micro agates and black, fine grained chamosite. The sediments have also been infused with what may be an orange, iron rich zeolite. It is soft and crumbles under a pin point.

The presence of sediment filled vesicles and clastic dykes in the mafic basalt host suggests that this locality may be near the contact between the lava of the Lake Shore Traps and the sediment in the Copper Harbor Conglomerate prior to lithification. This type of formation sometimes forms when lava flows over wet sediment and the resulting steam pressure drives the sediment into the basalt. (See child photos)

In agate collector jargon the specimen shown above would be called a "peeler". Due to weathering the banding delaminates and "peels" away, showing the three dimensional contour of the bands. The following quote mentions two interesting components found in agates:

"Agate, generally defined as banded chalcedony, is mainly composed of silica phases (i.e., α-quartz, moganite, opal-CT, opal-C, and opal-A) [1,2,3,4], with minor impurities, such as Fe compounds, sulfates, and carbonates [4,5,6]."

If moganite and/or carbonate is integral in some of the agate bands delamination may be the result of dissolution. Moganite has been described as being seven times more soluble than chalcedony and calcite would be soluble in rain water.

Reference: Xuemei Zhanz, Lei Ji, Xuemei He (2020) Gemological Characteristics and Origin of the Zhanguohong Agate from Beipiao, Liaoning Province, China: A Combined Microscopic, X-ray Diffraction, and Raman Spectroscopic Study, China University of Geosciences.

These chunks were found while looking through old boxes that I set aside years ago. During the 50's and 60's it was not uncommon to find old diggings where material like this was discarded. Sometimes while hiking, we would stumble over rocks hidden under the ferns. Looking closer you would see a shallow scooped out area nearby. The rocks were quite clean having been subjected to many years of rain fall. I picked up interesting samples and put them in boxes labeled "Lake Shore Traps" and forgot about them.

After many years of research trying to understand the mineralogy and geology of the Keweenaw, I found these specimens to be more interesting than I first thought, especially the two shown below. They are both quartz veins with casts of large calcite crystals. They suggest that at one time in the geologic past there were some very nice calcite crystals protruding into the open space in fractures. The specimen on the right has casts on both sides of the vein. Obviously the open space in the fractures eventually filled with microcrystalline quartz.

I have often wondered who dug these shallow pits and then discarded the contents. It seems like modern collectors would have kept the specimens. Perhaps some of these are holes that were left by the "greenhorn" prospectors of the 1840's in their rush to find copper.

The Meadow... This is a historic location in the Lake Shore Traps about one mile east of Copper Harbor. The photos were taken in 1977 but the location is now within a conservancy and collecting is not allowed.

Copper Harbor Conglomerate

The map above shows the Copper Harbor Formation in black. It is courtesy of the USGS in this reference:

Wolff R. G. and Hube N. K. (1973) The Copper Harbor Conglomerate (Middle Keweenawan) on Isle Royale, Michigan, and its Regional Implications, Geological Survey Professional Paper 754-B

Note: In older geological literature the formation and one of the main members had the same name, Copper Harbor Conglomerate. It has been changed to read, Copper Harbor Formation with two members, Copper Harbor Conglomerate and Lake Shore Traps. The Lake Shore Traps extend from Manitou Island in the east and follow the curve to the southwest. However, they terminate in Houghton County adjacent to the airport. The Copper Harbor Conglomerate continues on through Ontonagon County and on to the Wisconsin border.

Above Center…..are two clasts of red vesicular Felsite embedded in felsic sandstone at the water's edge near Copper Harbor. The vivid red color of the Felsite often causes it to be misidentified as jasper. Brown/maroon/red felsic clasts are abundant in the generic conglomerates that stretch for about 6,000 ft. from the St. Louis Conglomerate upward to the beaches at Copper Harbor. The conglomerates are interbedded with about 287 mafic basalt flows. Reference:

Cannon, W.F., and Nicholson, S.W. (2001) Geologic map of the Keweenaw Peninsula and adjacent area, Michigan, U.S. Geological Survey.

Below…..is a specimen from the St. Louis Conglomerate that shows a clast of vesicular Felsite in the lower right corner. This similarity supports the theory given in many professional papers that there was a highland southeast of the Keweenaw Peninsula that contributed felsic rocks down slope into the alluvial fans that eventually became a sequence of lithified conglomerates.

Clark Mine

If you were a tourist visiting Copper Harbor and asked a local what is there to see, he would certainly have mentioned the Clark Mine. It has been a tourist attraction since the 1950's. For the mineral collector it has also produced many interesting specimens including chunks of native copper and nodules of white datolite. The tall chimney with a tree growing at the top has been the subject of many photographs.

The white arrow points to the approximate location of the shaft. In the old days the shaft was surrounded with a snow fence. It was filled with rock from the dump but after many years there was some subsidence and more rock was filled in. The snow fence was not replaced.

The two photos below show the change in the rock piles from 1974 to 2011. Mine dumps all over the Keweenaw are being crushed for road fill. This has been going on for many years the reason being that there are no limestone quarries in the Keweenaw. When needed the mine dumps get crushed. One local told me sarcastically that "The runways at the airport in Houghton County are paved with datolite".

Below…..In the old days prior the metal detecting craze, large chunks of "mine run" copper could be found rather easily. In later years when the metal detectors started working the mine dumps the amount of "mine run" tinned out in a hurry. Of course I bought a detector and joined the fray.

A Story…..There is no doubt that metal detecting saved many fine copper and silver specimens from the crusher. Michigan Tech and the local gem and mineral club started to host the "Copper Country Retreat". It included several days of field trips that were of special interest to metal detectors. Four or five rock piles would be bulldozed to turn up fresh material. At a given time the piles would be opened to a throng of detectors. It was a noisy event with the sounds of beep, beep, ding, ding, and quack, quack all around you. Yes, some of the detectors sounded just like a quacking duck. I had a beeper but I always thought that the quackers did better than me.

The process of bulldozing the piles caused the rocks to be mixed with dirt making it impossible to see anything without a detector. This wasn't for me. I gave my detector to my son and went back to collection after the piles were washed with several hard rains.

Above left…..This is a typical sample of copper ore as found in the poor rock pile. The Clark Mine was one of the earliest mines operating in the Keweenaw. The miners were interested in high-grading masses of native copper and ore of this type was discarded. Large chunks of quartz and prehnite veins peppered with copper could be found on the piles.

Above right…..Copper in prehnite (5.5 X 2.8 cm). This is a section cut through the specimen on the left. It shows a bit of Keweenaw Pegmatite at the top.

Datolite…. In the early days of collecting (30's and 40's) Datolite was extremely plentiful at this location. At the main dump Datolite nodules were nearly all white. It would be very rare to find a nodule with color there. Datolite with pastel colors were found at the "swamp adit" north of the main dump.

There are about 37 datolite nodules shown in the three photos above. All of them were found clustered together in about one square foot of rock and dirt. When the shaft was sunk the datolite nodules were encountered near the surface. We always had the best luck collecting in small brush covered rock piles that were dumped early in the sinking of the shaft.

Clark Mine Swamp Adit

Manganese Mine

From the Keweenaw County beaches

The beaches of Keweenaw County are covered with pebbles and cobbles from various sources resulting in an extreme diversity of rocks and minerals. The Copper Harbor Conglomerate is composed of a variety of clasts that are held together by calcite cement. Weathering and wave action releases many of these into the freestone gravel on the beach. The fracturing and weathering of the nearby basaltic and rhyolitic flows including their amygdaloidal and vein content are also part of the gravel mix. Multiple glaciations deposited till from the Canadian Shield and the Lake Superior Basin along the beaches dropping an occasional erratic boulder.

The probable identification of the pattern on the specimen above was aided by the Mindat forum. The similarity with the genus Billingsastraea is significant, however, the specimen is composed of translucent chalcedony and, under the microscope, the interior coral structure is not apparent. This may be a cast that only preserved the exterior septum.

Reference: Ehlers G. M. and Stumm E. C., 1951, Corals of the Devonian Traverse Group of Michigan. Part IV, Billingsastraea, University of Michigan Press.

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Discuss this Article

17th Mar 2021 10:52 UTC Larry Maltby Expert

Thanks for the comment Keith.

I first saw Copper Harbor in 1950 and it has provided me with a lifetime collecting.

17th Mar 2021 16:15 UTC Steve Ewens

Larry,

Excellent!!!

What wealth of information.

Thank you for sharing many years of passion and research.

Steve

17th Mar 2021 13:29 UTC Paul Brandes 🌟 Manager

Incredible article, Larry!!!

This is the kind of writing the Keweenaw deserves...

17th Mar 2021 16:19 UTC Larry Maltby Expert

Thanks for the comments guy's.

This is a photo of our camp at Fort Wilkins State Park in 1950. My dad bought a rear axle from an old pick-up truck complete with springs. He had a friend weld an angle iron frame and built a plywood box with compartments for everything. On this trip I saw agates for the first time. A guy had a stand in front of his house and I bought a quart bottle filled with agates in water. I could see three nice ones pressed against the glass. When I got home and dumped my treasure in the sink, I had three agates and a bunch of beech stones. Non-the-less I became a rockhound.

17th Mar 2021 16:53 UTC Steve Ewens

Larry,

Have you ever considered publishing your specimen photograps?

I know you viewed an on line version of Hart Mountain Amygdales. A similar version could be self published.

I would be proud to own a copy.

Steve

17th Mar 2021 21:20 UTC Larry Maltby Expert

Steve,

I better stick with Mindat articles. I am working my way down the peninsula. I will be lucky if I finish before I "croak".

17th Mar 2021 18:11 UTC Allan Blaske

Excellent article, Larry. Especially the photographs. Wow! I first saw Copper Harbor in 1975 or so. I can still recall picking up that first chunk of basalt with zeolite-filled amydgules and still have that first chunk of copper i bought from a roadside stand! So I was a few years behind you. You really shouldn't post things like this. It only makes my desire (yearning?) to be there that much stronger! It's painful to be in southern Michigan in the glaciated wasteland of geology!

17th Mar 2021 21:12 UTC Larry Maltby Expert

Thanks Allan,

By getting there in 1950 I was able to see "Old Reliable" the Quincy No. 6 Shaft House before it burned in 1956. There was also a lot more poor rock piles along Highway 41 back then.

17th Mar 2021 18:26 UTC Alfredo Petrov Manager

Thank you, Larry. Great article. Brings back happy memories of a visit to Copper Harbor with George Robinson in the 1990s. He very kindly went far beyond the call of duty to take me to visit the Manganese mine after I expressed an interest in the mineral macfallite.

17th Mar 2021 21:13 UTC Larry Maltby Expert

Thanks Alfredo,

I learned a lot from George and from you. It was nice that Travis Olds gave me permission to use some of his photos from the Manganese Mine. His specimens added much more diversity.

18th Mar 2021 01:36 UTC Travis Olds Expert

Larry,

This is a wonderful compilation! The agates are so colorful and I love your photos of Keweenaw rocks and minerals in situ.. I am happy my photos enhanced your article. Just note that photo 241260 of pyrolusite is from the dumps of a different "Manganese mine" in Marquette County, that is related to the "Aetna" and several other surrounding explorations/mines.

18th Mar 2021 12:56 UTC Larry Maltby Expert

Thanks again Travis,

I will correct the location on the pyrolusite soon.

My favorite specimen of yours is the orientite/macfallite "creamsicle". It is one of a kind. With the closing of the hole I doubt that anything like this will ever be found again.

"Fixed"

18th Mar 2021 14:32 UTC Tony L. Potucek Expert

Really well done, Larry! Glad you haven't croaked yet! Ha! Like you, I continue to impart whatever knowledge I have accumulated over the years regarding my collecting around the Western USA and Mexico. Thanks for taking the time to post your photos and comments!

19th Mar 2021 11:29 UTC Larry Maltby Expert

Tony,

I am trying hard not to "croak" but it seems like I am getting "hoarse'.

18th Mar 2021 16:19 UTC Andrew Debnam 🌟

great article Larry, I admire the work you put into it.

18th Mar 2021 18:50 UTC Tony Albini

Larry, superb job! Your mention of stromatolites which I have commonly seen referred to as slime, scum etc. People forget these were the organisms that pumped the oxygen into our atmosphere and instrumental in precipitating iron out of the oceans to form large iron deposits.

19th Mar 2021 13:30 UTC Rolf Luetcke Expert

Larry,

Wonderful article and so much more than just a mineral tilt to it, thanks, great read!

21st Mar 2021 00:00 UTC Dana Slaughter 🌟 Expert

Outstanding article Larry! Your contributions are a real asset to the mindat community. Thanks for sharing your photos and knowledge.

Respectfully,

Dana

21st Mar 2021 19:36 UTC Barb Matz

Great Article! Takes me back to my years at MI Tech in the 1970s and numerous subsequent visits, all of which incorporated much poking around in various mine dumps and other localities. I'm looking forward to the continuation of this series.

And that was not just any professor at the rock shop ... Doc Berry was well known (mostly feared, sometimes also respected) by all Tech freshmen!

11th Apr 2021 09:49 UTC Larry Maltby Expert

Dana and Barb,

Thanks for the comments. Hopefully the next article will be on the southern half of Keweenaw County.

11th Apr 2021 15:46 UTC Keith A. Peregrine 🌟

Thank you for sharing this Larry. Always enjoy what you share!

15th Apr 2021 15:34 UTC Kyle Beucke 🌟

Larry,

I am only halfway through this but I wanted to say you did an awesome job. I usually do not seek out "collecting" stories. Your excellent storytelling and writing and really beautiful photographs make it easy to imagine experiencing these things firsthand. I can imagine seeing La Roche Verte as a kid and I bet that would stick with you in a similar way a first experience with a hot spring or a dramatic road cut stuck with me. This is clearly an interesting and beautiful area and you did it justice.

Kyle

16th Apr 2021 14:17 UTC Larry Maltby Expert

Keith, thanks,

I went back to your articles for another look. Neat stuff, especially the silver crystals in the float copper. I remember seeing that specimen. The silver crystals were in a vug in the copper, but it is amazing that they survived the erosion that float copper experiences.

Kyle, thanks,

I read all of your posts. I have developed an interest it alterations, replacements etc. and you get into a lot of that. Your latest article on The Como mining district, Lyon County, Nevada is a great example of that.

Larry,

22nd Apr 2021 01:42 UTC Paul Spagnotti

I was born and raised in Ahmeek. There are more places than just Copper Harbor for agates. What about Agate Beach just up the road from Copper Harbor? All you have to do is walk around the beaches and you will find agates. Don't limit yourself to Copper Harbor. If you are planning on going to any of the old rock piles; you can forget that; most of the rock piles have been ground up for road work, if not that, then private.