- Recreation Area, Rockhounding
- General info
Crystal Park is a unique recreation area at an elevation of 7,800 feet in the Pioneer Mountains in southwest Montana. The Butte Mineral and Gem Club maintain mining claims at Crystal Park open to the public for digging quartz crystals (rockhounding in Montana). You are welcome to dig for quartz crystals here but are asked to follow the rules of the Park. The park is open from May 15 through October 15, but those dates are subject to change depending on snow and road conditions. There is no charge, although donations for support of operations and maintenance of the site are welcome.
Like most of the eastern Pioneer Mountains, the “country rock” or bedrock at Crystal Park is granite. About 68 million years ago, the Pioneer Batholith intruded the area, pushing up molten granite to form the Pioneer Mountain range. The granite was about 300º C or approximately 600º F. As the granite cooled, super-heated water circulated through it, carrying quartz, pyrite, and other minerals in solution. As the granite and the water continued to cool, the minerals precipitated out and were deposited in veins and cavities (called “vugs”). The molten granite continued to cool and solidified for several thousand years
Later, glaciers, surface and groundwater, weathering, and other erosional processes exposed the minerals and crystals to air and groundwater. The original crystals remained unchanged, but when the rock temperature was 30º to 50º C, and iron (from pyrite) was available, amethyst quartz crystals were formed. Amethyst crystals sometimes formed directly on another colorless crystal.
Quartz crystals at Crystal Park seem randomly distributed because weathering of the granite has freed them from veins where they formed. Careful digging can sometimes expose traces of veins seen as reddish-brown zones in the light-colored granite. By tracing remnant veins, “pockets” of crystals are sometimes found.
About 30 of the nearly 200 acres set aside for crystal digging are currently open. Digging areas are a short walk from paved parking. Facilities include a hand pump water well, three picnic sites with tables and grills, information signs, toilets, and a paved trail with benches and an overlook. The facilities are designed to be universally accessible. Crystal Park is open for day use. There are Forest Service campgrounds along the Scenic Byway to the north and south of Crystal Park. A host is usually present to assist visitors, maintain the facilities, and ensure the rules are followed.
Information on digging for quartz crystals is available at the Park. You will need to bring your own tools. For digging, a shovel, hand trowel, gardener’s hand cultivator, and gloves are useful. A daypack to carry your tools in is handy.
Reprinted from Forest Service brochure.
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