The Minerals of Bear Lake, Ontario, Canada

Near Tory Hill, Ontario, Canada

 

(Please note this site is now under private ownership and,

as such, collecting minerals at this site is forbidden)

 

by Michael Walter

 

Apatite specimens like this one, photographed for Rock and Gem Magazine, are not all that uncommon at the Bear Lake diggings near Tory Hill, Ontario, Canada. 

                        Fluorapatite                                                        Fluorapatite

 

As I walked onto the wooded hillside it quickly became evident that thousands of rock hounds had been at work there. Narrow but deep channels had been dug into the soil throughout this stretch of mixed hardwood forest. Most descended at a slightly inclined angles through the glacial till and then into the native bedrock below. Later, I was to discover that these channels were all that remained of calcite veins (perhaps dikes as they are locally known) that had their calcite etched away by the natural forces of chemical weathering and erosion.

This was my first exposure to a site called the Bear Lake Diggings. Previously this location had been referred to as the Maddill Road Occurrence. The Bear Lake site is a source of various crystals which not only show text book form but grow to enormous size. Within the area soil and from within the previously mentioned calcite veins one can find mica, feldspars, hornblende series minerals, apatite and titanite. These are the most common specimens...and I really mean common. Whether you start a new digging or look through the tailings left by previous collectors you are bound to find crystals. Perhaps a story would more clearly illustrate this point.

The first time I visited the Bear Lake site was in 1991. Two other collectors were there squirming deep within one of the trenches. Being rookies at this site my Father and I immediately began examining surface showings. To our surprise small green apatite crystals seemed to be in all the the piles left behind by other collectors. It was unclear to us why they would leave behind perfectly formed, often terminated crystals between 1/2 and two inches in length. We wasted no time in filling a cardboard flat with nice specimens.

After an hour or so we had a chance to speak with one of the two subterranean collectors we had seen earlier. He described to us how the better specimens are weathered out of the calcite and then settle to the bottom of these calcite seams. Though sometimes difficult to get at this was where the best material was to be found. Was he ever right. Opening a cardboard flat he proceeded to show us what a good specimen looked like. Apatites from 3 to 6 inches in length, beautifully formed feldspars and the specimens they were really after, dark brown titanites. These lustrous blade shaped crystals were gorgeous. They had single blades as large as three inches and intricate clusters of crystals just as large. Some of their specimens were combinations of all these minerals as well as darker minerals such as biotite and hornblende. Man, was I ever excited.

The day was reaching its end, and the other collectors encouraged us to dig in this trench as they would be returning home that evening. For me, that was a very restless night of sleep. I kept wondering what treasures we would find deep in the darkness of that trench the following day.

Once the morning broke, and the coffee had been drank, we made the short trek from the campsite in Wilberforce to the collecting area. The trench where we had intended to dig was just as it had been left the day before. No other collectors were here besides ourselves. I slinked my way into the trench and came to the realization that being skinny is a benefit when collecting minerals at this location. The trench itself was only 20 to 24 inches wide in any one spot. I could handle the trench width but what made matters truly difficult was having the seam decent at an angle which made movement awkward and uncomfortable. At a depth of about 12 feet I reached the bottom. The walls and bottom were both composed of a light pink calcite. I squirmed my way to one end of the trench where I encountered a wall of soil. This was where I needed to dig. No sooner had I stuck my trowel into the soil then crystals of apatite began to appear. These were not at all like the ones we had found on the surface the day before. Some were up to eight inches in length though most averaged three to four. These were much larger and often double terminated. They were everywhere in the loose soil. As they were uncovered I placed them in a small bucket to be pulled by rope to the surface. On occasion large feldspar crystals up to five inches in diameter were encountered. Also, small one to two inch titanite crystals and clusters of the same could be found though they were much less common.

The digging conditions were difficult due to the space restrictions, but my main concern was with the over burned of dirt which grew more hazardous as I continued to dig. This became an issue because all of the minerals were to be found in the lower foot of dirt right next to the unweathered calcite in the base of the trench.

After the overburden became to risky for my liking, and the trench narrowed beyond my ability to dig further, I decided it was time to call it quits at this spot. Once on the surface I surveyed the minerals recovered from the my short time underground. It was hard to believe but in several short hours I had removed approximately 20 square feet of dirt. This is not much for a morningıs effort. The shocker was that that small amount of soil had held 15 to 20 flats of specimens.

This was my first experience with the Bear Lake site and I hoped not my last. From that year until the summer of 1995 claim disputes lead to this area being off limits to collectors. It was not until 1995 that the Chamber of Commerce for the town of Bancroft, Ontario purchased the land on which this site was found. The Chamber developed guidelines for collecting and began to sell permits to collect at the newly named Bear Lake diggings. They also began conducting field trips lead by their staff geologist Chris Fouts.

Here is yet one more memorable experience I had at this site in 1996. Another collector called us over to see what he had found in the trench where he had been digging. This is fairly common at Bear Lake. People commonly uncover some pretty impressive crystals and, of course, want to show them off. This collector had not found a specimen but rather had found a cave full of specimens. The opening he found was approximately 10 feet deep and about 4 feet wide in its diameter. With a flashlight I inspected the mineral incrusted roof of this opening. Impressive apatites, feldspars, hornblendes and titanites hung downward like stalactites.

Thinking I might share in this collectors good fortune I moved up the hill and began digging about 40 yards away but where I thought an extension of the same seam would be. After digging through several inches of soil I hit solid rock without any weathered seams in the bedrock. I removed soil in all directions eventually finding a small crevice the size of a pencils diameter. When the rock layer was tapped with a crack hammer that exciting hollow sound rang out. Using a six foot crowbar large chunks of rock could be removed reviling the underlying pocket. It was not huge by Bear Lake standards. The crystals were well formed slender hornblendes. Oddly enough no sign of any other form of mineral was present in this pocket. When I was done an area the size of a small wash tub had been excavated. One large cluster of these long hornblendes (actually fluo-magnesio-kataphorate) crystals was removed.


Though I am describing this site from the point of view of a serious field collector this is a great site for those new to mineral collecting: permission is easily obtained through the purchase of a permit at the Chamber of Commerce, the site has plenty of area to explore, the location is relatively safe, plenty of specimens can be found using various collecting methods and most of the area lies within a well shaded forest. Children will love this site but care should be taken not to allow them down into deep trenches without strict supervision. The only drawback that comes to mind regarding Bear Lake is the insect life.The diversity and numbers of insects is not lacking. One should be prepared for mosquitoes, black flies, "no-see-ums" and deer flies depending upon the season.

The Minerals

Apatite
Apatite is by far the most common mineral at Bear Lake. An enormous range of crystal sizes are present. In the weathered soil complete crystals up to eight inches can be found. Larger crystals are present but are seldom found in one piece. One will often find two or three large chunks of a broken crystal lying end to end in the bottom of the trenches. It seems the largest crystals tend to cleave across their ³c² axis as they weather from the calcite. Perhaps they are more readily affected by the weight of overlying soils or maybe their own mass accounts for their seldom being found in their entirety. Whatever the case these large crystals are difficult to extract no matter how careful the collector works.

Occasionally, monster crystals of apatite in the two to three foot range are discovered. I say discovered because it is actually rare to recover them. Usually they are found embedded within the wall rock of calcite. In any case they usually crumble into tiny unrepairable pieces when attempts are made to remove them.

The first monster apatite I came upon at Bear Lake was exposed its full length in an accessible area of wall rock. It really looked like if I were patient and chiseled completely around the crystal it would come out whole. This two and a half foot beauty was about 12 inches wide and probably weighed in the area of 40 pounds. Several hours later it became apparent that this crystal was not going into my collection. The largest piece I removed was a chunk about two inches square. Not only will large apatite crystals from this location crumble under their own weight, they will tend to be loaded with thousands of micro fractures which limit the possiblilty of their removal.

As for quality specimens they tend to be the loose crystals found in the soil. Often double terminated these crystals have been weathered from their homes within the calcite matrix within the regions dikes. The terminations on the apatites from this site, and others from the Bancroft region, look like melted candle wax. Well formed termination faces are a rarity here. The other crystal faces which comprise the prism of the crystal are often smooth and lustrous.

Bear Lake apatites are normally various shades of green and on occasion a reddish brown. Their clarity is limited due to extensive internal fracturing along cleavage plains. In better crystals gemmy areas are present. Some of these are large enough to be faceted into small gems.



Feldspar

I have never thought much about feldspar as a collectorıs mineral until the past few years. The diversity of color, form, and levels of clarity among this common mineralıs crystals is quite impressive. The mineral found here at Bear Lake is actually orthoclase with secondary (overgrowths) of albite. The crystals are often well formed and large. Specimens weighing many pounds are not uncommon.

Hornblende
Hornblende crystals here are found in enormous sizes. Individual crystals can weigh many pounds and be tens of inches long. The actual name of this amphibole has been hotly debated with limited agreement. Chemical tests have shown some of this material to be fluo-magnesio-kataphorate. For the sake of simplicity I will refer to it as hornblende.

Hornblende is such a common mineral that we seldom give thought to it as a collectors mineral. Perhaps the reason for this is that it seldom forms good crystals. The ones found at Bear Lake are exceptional. They reach staggering sizes, can be high in luster and take on a variety of shapes. Some are long and slender while others are short and equant. They form amazing clusters, can be found in single crystals and are common associates with any of the previously mentioned minerals.

Titanite
Titanite is the real treasure offered at Bear Lake. This mineral forms deep brown, opaque crystals that are often translucent on edge. These specimens are sought after by most collectors who visit the site. Their form looks much like the shape of an ax blade. When fully terminated they have an ax like edge on all sides of an almost circular crystal. Crystal clusters of this mineral can be quite dramatic with sharp disk shaped blades radiating in a multitude of directions.

Normally, The titanite specimens are small compared to other crystals from the location. Clusters and single crystals of three or four inches would be considered large. However, like other crystals from this site, monster sized crystals are sometimes encountered. One such example can be seen in the Bancroft Area Chamber of Commerceıs mineral museum. This beauty is a fully terminated crystal the size of a small dinner plate.

Finding good titanites takes patience. Not all seams will hold this mineral. Sometimes it can be found attached to the wall rock, especially in small pockets. Often titanite will settle to the bottom of the seams like the other minerals such as apatite. These mineralıs densities tend to be greater than that of the surrounding soil in which they are contained. As a result they sink over time to the lowest level within the seam. This serves to concentrate mineral specimens at the greatest depth.

Titanite is often found in combination with other minerals. Its most common associate is with feldspar, though it is also found with biotite, apatite and hornblende. Some of the most aesthetic mineral specimens from Bear Lake are combination pieces composed of titanites and feldspars. The dark titanites can be found penetrating the cream colored feldspars in interesting patterns.

Several collectors with whom I have spoken swear by a method of collecting which seems contrary to the norm. As previously mentioned, crystals tend to settle to the bottoms of these soil filled trenches due to their densities being greater than the soil in which the are found. These collectors looks for titanite crystals in the top foot or so of the soil in these seams. They explore the forest floor for linear depressions in the soil. This may indicate the presence of an underlying seam. If they excavate the spot and find a seam extending downward at an angle, instead of vertically, they would then only dig out the uppermost soils and find titanites within these. I have only had success using this approach on one occasion. I found a depression and within several minutes of digging had two large titanite blades. Because the seam extended downward at a fairly gentle slope these crystals had not had the opportunity to settle very deep into the seam. I was able to find where both crystals had formed on the hanging wall of the seam, broke away, and subsequently settled to the foot wall below.

Biotite
Large and well formed crystals of biotite are common as a wall rock mineral. These hexagonal books can reach 10 or more inches in diameter. Though most minerals collectors tend to ignore the mica from this (and most) locations, some have been known to keep the larger books. Kids love this mineral, too. It seems they can find great enjoyment in peeling off layer after layer. Its like having a rock that sheds its skin.

Leucoxene
Another mineral found here is leucoxene which is a pseudomorph of titanite. It is not uncommon to find blades for titanite that look like they have a light grayish white coating over part or all of their surface. This is not a coating but actually a replacement of the titanite by the mineral leucoxene. These specimens will have a much lower luster than the original mineral but have the same sharp crystal form.

Other minerals are occasionally encountered at Bear Lake. One of the more unusual ones was discovered when I was home cleaning specimens from a recent collecting trip. I was washing off a large poorly formed apatite crystal with the hose when I noticed a hole in its side. Because so many of the apatites from here can be poorly formed I did not immediately take much notice of it. Once it was dry I picked it up for closer inspection. Little wood chips like you would get from using a chain saw were falling out of the hole. This still did not surprise me because there was lots of cut timber on this property from its recently being logged. What finally got my attention was when they kept coming out in greater numbers. Had a insect stored these in here for a home? At last the light went on completely when I realized that these were not wood chips. They were floater crystals of light brown calcites! Hundreds of them had formed in this opening in the apatite crystal.

Bancroft is approximately 240 kms west of Ottawa, 240 kms north-east of Toronto, 110 kms north of Belleville, 110 kms north-east of Peterborough, 145 kms west of Pembroke, 63 kms east of Haliburton

 

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