Tomahawk Basin, Colorado: Fluorite

By webmaster at 11:02 am on April 24, 2008 | 1 Comment

In the mid-1970’s I spent some time working in SW Colorado in the La Plata Mountains near Durango. This area has produced significant gold (the Bessie G mine, for example, was active at that time) and has been investigated for its porphyry copper potential and uranium as well.

The Tomahawk Mine and basin are located above timberline in the western part of the complex. Rocks in the area include a variety of intrusives and metamorphosed sediments that form the high ridges and cliffs around the head of Tomahawk Creek. The Tomahawk mine produced gold in the last century. At the time I worked in the area there was still a very thin, rich vein containing visible gold accessible (if you were a skilled rock climber) on the cliff face at the creek near the mine ruins.

tomahawk basin from southeast

Above: Tomahawk Basin seen from high ridge to SE.

Below: Tomahawk Mine structures in 1975.

tomahawk mine ruins

What passed for a road ended a few hundred yards west of the mine at a drill site located near a small intrusive complex. Talus from the high cliffs to the south of this intrusive contained scattered vugs that were mineralized with epidote, quartz, K-feldspar and rare fluorite. The fluorite crystals were simple octahedrons of a rich violet color. Their maximum size was about 2 mm.

I have always thought that it would be worthwhile to investigate the area for the source of the fluorite. Perhaps there are larger cavities and better crystals in the larger talus or lower cliff faces a few hundred feet up and to the south of the intrusive. Are there any of you energetic young collectors interested?

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Brazilian Beryls

By webmaster at 5:47 pm on April 14, 2008 | No comments

During our trip to Brazil in 1988 we visited Belo Horizonte, a perpetual hub for the gem and mineral trade in Minas Gerais. We saw a number of dealers with wonderful specimens but perhaps the most memorable was a non-descript office and showroom where we saw the most unexpected and amazing group of beryls. Apparently, these crystals had been found a short time before during road construction and had ended up in the hands of this dealer. Unfortunately, I do not recall his name.

27 kilos of gem beryl

The six crystals weighed a total of 27 kilos; all were nicely terminated and very gemmy and of good color. In the picture they sit on their terminations. The golden beryl was said to be from the same find, but is was not clear if it was actually from the exact same site as the aquamarine crystals. Asking price: $1,000,000.00. We have always wondered where these crystals ended up.

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Paraiba Tourmaline Mine, Brazil, 1988

By webmaster at 3:39 pm on April 9, 2008 | 5 Comments

In the spring of 1988 we spent a month in Brazil. We were looking for the usual mineral and gemstone specimens, and wanted to stock up on quartz and things like spheres for the ‘crystal craze’ that was in high form then. Our primary purpose was more long-range, however. The previous year a friend of ours who lived in Sao Paulo had visited the states and had brought with him several faceted tourmalines from the Paraiba occurance. These were of the best tourquoise color and attracted a lot of attention as the area was little known at the time. He wanted a geological evaluation of the mines so we agreed to follow up and do a field check of the producing area. We all wanted to see if there was any possibility of acquiring either a source or ownership.
Arrangements were made to meet with one of the developers of the property. We traveled to Paraiba state to meet him, flying into Recife on the coast and then to Campina Grande where we met Hector. Hector was a well-to-do man by local standards, a road repair contractor, who had sold most of his business equipment in order to pursue mining the tourmalines at Paraiba. We met him at a hotel in a small town where we looked at bags of stones, mostly small fragments of crystals with mixed quality and color and with none of specimen quality. In the morning Hector took us further into the ‘wilds’ stopping to show us a home he was building for his family. It was very basic by our standards, cement floors and walls, one water source and a bathroom separated from the house. We drove in a small jeep some 25-30 Km, over dirt tracks that would have been impassable in wet weather. At one point he leaned on the horn in the middle of nowhere and we all wondered why. As we crested a small hill, there was a gate across the road and a small boy was pushing it open. Our driver slowed, but never stopped, and handed the boy a bill, maybe 50 cents, that would make his week.

Teri, Hector, Steve to Paraiba

We arrived at the mines and the small village of Sao Jose da Batalha. It was a typical one street village, with mostly stone or cement homes with red tile roofs and large window openings with no glass or screens. Goats and pigs and a variety of dogs made themselves at home just about everywhere, including inside some of the homes.

trench north end paraiba mine hill

The mines all followed a very clear structure that crossed a hill, probably covering 40-50 acres. From the crest of the hill the structure could be seen in the distance revealed by the white waste rock around pits and trenches in the associated pegmatite. According to Hector, there were more locations for gemstones on the structure, but none had the color of those at the site we were evaluating. On the hill there were large trenches and open cuts, some clearly quite old. These showed areas with wonderfully colored, zoned pink and tourquoise tourmalines in matrix. Fine specimens but not the gem crystals we were looking for. As I recall, there were some very active wasps in the area as well. To compliment the wasps there were some attractive but toxic caterpillars on the bushes. Teri approached one of them and was warned the she would have ‘24 hours of pain’ if she touched it.

Steve examines tourmaline

There were two active workings on the hill at that time. One, a vertical shaft, was producing very little. The miners offered me a tour but after looking over the way they maneuvered down the shaft (20 meters deep) with only an old-looking rope attached to a flimsy tripod of sticks and what might have passed for steps in the walls, I declined. Twenty years ago I was much more agile and a lot lighter but still no match for those guys.

miner entering vertical shaft

The second workings were more productive and had been open-cut but, following a rock slide, were contained in an adit designed to intercept the pegmatite under the previous surface openings. There was one miner working with very basic hand tools and progressing a few feet a week. Hector wanted enough money to get some drilling equipment and a diesel powered compressor to speed things up. Everyone agreed that the rare crystals of gem quality were “limpia, limpia” and as big as our fingers. Following the tour we retired to Hector’s town home where his mistress (he was a two family man) had prepared rice, beans and some sort of meat. We talked about the problems of obtaining mining rights as ‘outsiders’ and it really came down to trusting a local, Hector in this case, with a lot of money. It is a bit more complicated than that, but it became clear that inspite of the obvious potential, we would have a difficult time gaining a realistic controlling position there. Over the next few years many fine crystals and gem stones were produced from these mines. We never did find out if Hector was able to continue with his operations or if he was part of this success.
We returned to Campina Grande for the evening. After a nice meal and a stroll around the downtown shopping area, occasionally passing open-air coffin vendors with products displayed leaning against the store fronts, and returned to the hotel. We left for Recife and points south in the morning.

Steve Rose

Filed under: Rocks & Minerals, Brazil Tourmaline5 Comments »

Mclaughlin Mine, stibnite

By webmaster at 4:30 pm on April 8, 2008 | No comments

In the early 1980’s development work at the Homestake Mining Company Mclaughlin Mine project at the junction of Napa, Lake and Yolo counties in California turned up some nice stibnite specimens. Drill core from some areas contained scattered stibnite in veins and vugs, and in one case, stout crystals up to 3-8 cm in a wide calcite vein. The best specimens from this period, however, were found when a bulk sample decline was sunk in a near-surface part of the ore body. This work was designed to sample an area of the silicified Knoxville formation mudstone, a significant gold host on the property. Numerous quartz-chalcedony veins in the workings contained stibnite in masses, radiating sprays and in small vugs. The best specimens showed bright, needle-like sprays up to 3 cm in open vugs lined with bright micro quartz.

The muck (bulk sample) piles provided lots of fine samples, sometimes in masses of radiating crystals up to several pounds. The exposed faces in the decline were great for finding vugs, but were dangerous and usually only accessable after a blast when the fumes were sure to cause a nice ‘nitro’ headache. A contract minor was severely injured by rockfall at the working face during this period.

There are still a few of these specimens around; there should have been a lot available from the pit as it progressed, but I only have a few remaining. One is pictured here.

stibnite specimen

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Welcome to the 10xminerals.com blog!

By webmaster at 4:26 pm on April 2, 2008 | 2 Comments

This blog will be a site for sharing information about minerals, mineral collecting and related subjects for anyone with an interest. I look forward to hearing from others with news, collecting site information or those who just want to chat. I have personal experience in many areas including the midwest, west and some in the eastern U.S. but most current collecting is in Nevada and is somewhat limited to a few ‘old favorite’ sites.

I will be posting anecdotal information about some of the areas where I have had success or found things of interest over the years. I have a wide-ranging interest in things natural science, so if you are thinking of anything related, please send in a note.

Many thanks to Judith Harlan of harlaneditorial.com for her encouragement to start this blog. We are novices but expect to be ‘cruising right along’ in no time. Anyone thinking of starting a blog and looking for very professional help, please contact Judith. We’ve listed her link in our blogroll.

Steve Rose

Filed under: Rocks & Minerals, Welcome2 Comments »