B is for Butte

And bornite, barite, and Bluebird

Big Butte, to the left of the Anselmo Mine headframe, is part of the Lowland Creek Volcanics, 49-53 million years old, later than the mineralization in the 76-million-year-old Butte Granite.

Some mineral collectors are “systematic,” which often means aspiring to one of every mineral (as in Dana’s System of Mineralogy). Other collectors have definite specialties, such as one or several particular species, just arsenates, only orthorhombic minerals, one or two localities, and so on. I’m far too disorganized to be “systematic,” and fundamentally I’d call my collecting style “eclectic” or even random. Or maybe you might be charitable and just say “well, he specializes in 27 specialties.”

In any case, I certainly have a focus on Butte, Montana, USA, because it’s where I live, at the corner of Quartz and Crystal Streets (Granite and Porphyry might have been more interesting but those two streets are parallel and do not intersect).

Butte’s geology, mineralogy, and history (ethnic, labor, industrial, cultural, architectural) can’t be synthesized in a few hundred words (or a few hundred thousand, including 400 articles I’ve written on Butte history for the local newspaper), or even a few hundred books, so this post is just a vehicle for some of my favorite eclectic specimens or in some cases favorite photos. I hope it’s not too many!

Calcite, like fluorite and barite, is widespread in the Butte District, but not abundant.

Pink barite, unusual feathery habit

This silver was probably mined about 1988-1992 in the failed attempt by New Butte Mining to rejuvenate the silver deposit. Butte is the third largest historic silver producer in the world, after Potosi, Bolivia, and the suite of districts at Kellogg-Coeur d’Alene, Idaho.

Tan material like the coating here is often called ‘manganoan calcite’ or siderite, but Raman analysis was pretty clear that it is dolomite in this specimen.

Argentite in the old labels refers to acanthite, as all argentite inverts to acanthite at 177°C. The bits of acanthite here are pseudomorphs after argentite.

Tiny iridescent bornite on pyrite octahedrons

Little smoky quartz crystals in aplite of Butte Granite, Bluebird Mill site, west of Butte. Most are about 1 cm.

These malachite balls are probably post-mining.

Slag brick, pre-1930, probably pre-1900 from unknown Butte smelter. Found at the corner of Quartz and Crystal Streets in 2023 (no idea how it appeared there, just lying on the street).

The word “butte” is French, used for a prominent, often isolated and steep-sided high point. Apparently it was introduced in English by Lewis and Clark in their journals in 1805. In geomorphology you see it sometimes equated with a mesa or vice versa, but to me a butte is pointy and narrow, and a mesa has a flat top and is wide. Just how narrow the mesa’s flat top has to be before it’s a butte is a frequent semantic argument. The word was applied to Big Butte, the hill on the west side of Butte, in 1864 and quickly became the name of the town.

Some of the photos above are in my booklet for tourists, “Butte Rocks.” If you are interested here is a PDF of it. I did this in 2019 simply because there was no such thing available, which seemed to me unfortunate. During the tour guide phase of my life, 2006-2016, I talked geology and Butte history to more than 25,000 visitors, which encouraged me to think such a booklet might be useful. Hard copies are available at various locations around Butte.

Butte Rocks

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