New Mexico Mineral Symposium — Abstracts

The Thomas Range is internationally known to mineral collectors. Although it is the type locality for bixbyite, weeksite, and holfertite, it is more well known for its sherry-colored topaz crystals. The best crystals of pseudobrookite are found in the Thomas Range. Other mineral species include almandine, red-colored beryl crystals, calcite, ferrocolumbite, fluorite, hematite, ilmenite, quartz, and opal. With some exceptions, most of these minerals are found in a lithophysae-rich rhyolite.

There are numerous places in the range where specimens can be found. A few small books and many articles have been written about the occurrences.

Maynard Bixby, a good prospector, discovered bixbyite in the range in the late 1800s. The type location is "Maynard's claim," located on the east side of the range. Some of the range's finest topaz has come from here, with crystals and groups over 5 cm. Associated minerals are acicular microscopic topaz, drusy quartz, specular hematite, and hematite pseudomorphing garnet. This is an active claim and is posted with "keep out" signs.

There is a shallow gray knob of rhyolite immediately east of this claim. Some prospecting has taken place resulting in the finding of quartz-included topaz crystals to 3 or 4 cm with small bixbyite crystals to 3 mm and occasional very small holfertite prisms. At least 2 small 3-4 mm red beryls were also found.

The Autunite #8 mine, a uranium prospect, is located on the southeast side of the range. The rock here looks more like a welded rhyolite or andesite. There is local faulting, mineralization, and alteration. The uranium mineral weeksite was discovered there associated with highly fluorescent hyaline opal.

Holfertite was recently described from a pit on the west side of the range, in Searle Canyon, recently renamed "Starvation Canyon." It occurs as yellow to orange long prisms, to 2 mm, which are sometimes hollow. Most of the holfertite crystals are found on quartz-included topaz crystals that are usually 2-4 cm in size. Sometimes the holfertite is found attached to, or near, specular hematite or bixbyite cubes.

Pseudobrookite is found here, but the crystals are usually < 1 mm. Rare dull-black prisms of ferrocolumbite were also found. An adjacent pit had specimens of drusy amethyst. A couple of decades ago Eugene Foord wrote a partial description of a Ti > U silicate mineral from Topaz Valley. Because holfertite has U > Ti could the crystals found in Topaz Valley be a different species or were the data incorrect?

Three or four years ago someone blasted out an area on the north side of the range, about 3 mi west of Dugway Pass. This fresh white rhyolite is easily seen from the road. Apparently the name of this place is the "Solar Wind" claim. Pseudobrookites to 1.5 cm were found with small pink-colored topaz. Small bixbyites were found, although it is rumored to have had some crystals that reached 2 cm!

A place called "Topaz Valley," at the southeast corner of the range, is an area frequented by most collectors. Most of the crystals are small, but there are rumors of red beryl to 3 cm, topaz to 5 cm, etc. Other minerals are pseudobrookite, specular hematite, the holfertite-like critter, and rumored almandine. Countless sun-bleached colorless topaz crystals have been picked up off of the ground in the last century. These are now harder to find. There also used to be countless specimen-rich boulders that could be broken up with heavy sledge hammers. Most of the convenient boulders have now been reduced. However, the valley has its name for a reason, and countless specimens remain to be collected. It just takes more work and more patience.

The range's best bixbyite is reputed to be from a claim somewhere south of Dugway Pass. That, and the world's best durangite locality, were not visited by the writer because he could not find them. Sometimes getting lost can have its own rewards. For instance west-northwest of the holfertite pit an area rich with topaz was found. South of Dugway Pass a less-rich topaz area was found. Basically, if one goes hiking about in the Thomas Range you will eventually come across something interesting.