Quartz

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Lustrous crystals of smoky quartz coming off matrix. In good condition. Collected in the 1980s. Jefferson County, Montana, contains pegmatites associated with the Boulder Batholith that formed during the Late Cretaceous period, approximately 70 to 80 million years ago. These coarse-grained igneous rocks crystallized from the final, water-rich remnants of magma deep underground, creating a slow-cooling environment that allowed large, well-defined crystals to grow within open pockets. Historically, these pegmatite districts, including areas near Whitehall and Pipestone Creek, were prospected during Montana's mining booms for industrial minerals like feldspar and mica, as well as smoky quartz. The dark coloration of this quartz is a result of natural, low-level gamma radiation from surrounding elements, such as uranium and thorium in neighboring feldspar, which over millions of years disrupted the crystal lattice and activated aluminum impurities within the silicon dioxide structure to turn the quartz dark-amber to near-black.