New Mexico Mineral Symposium — Abstracts

Located in southwest Montana, this rugged mountain area has produced pegmatite minerals for more than a century. The pegma-tites, with few exceptions, are small isolated finds that are worked out in a day or two. A few deposits such as the Pohndorf mine have produced world-class mineral specimens such as amethyst scepters on smoky quartz prisms and tourmalinated smoky quartz.

The crystals are found in miarolitic cavities in the Butte Quartz Monzonite and other granitic rocks of the Boulder batho-lith. Although the area of occurrence is large and will produce specimens for centuries to come, finding a pocket is a difficult task that involves both physical effort and skill gained from years of experience. Minerals found to date include:

Quartz - common as smoky quartz, amethyst scarce Microcline - common as white crystals
Albite - clevelandite scarce
Schorl - common
Almandite garnet - scarce
Epidote - common in the Toll Mountain area Sphene - scarce
Limonite pseudomorphs after pyrite - scarce Elbaite - rare, two small finds have been made
Danburite - rare, two crystals found in a single pocket Beryl - rare, a few small crystals found
Axinite - two small but prolific deposits found recently Allanite - rare, a few one-inch crystals found

In addition to the pegmatites, Jefferson County has produced fine specimens of quartz and ore minerals from the metallic veins of its many mining districts. Minerals include:

Barite - three occurrences have been prolific producers Quartz - the Japan twins from the PC mine are spectacular
Silver - native silver and silver sulphides were common specimens found during the 1880's when much bullion was produced
Gold - placer deposits abound where the gold has accumulated in rivers and streams; hard-rock mining is still active
Cassiterite - found in the Boulder River with gold

Slides will show the pegmatite minerals in detail and the talk will conclude with an overview of Jefferson County mineral districts and outstanding mineral specimens.