Abstract We summarize the geologic settings, generalized geology, and inferred conditions of talc formation for two major deposits in southwestern Montana. Imerys Talc operates the Yellowstone Mine in the Gravelly Range. Barretts Minerals Inc., a subsidiary of Minerals Technologies Incorporated, mines talc from two large deposits—the Regal and the Treasure—in the southern Ruby Range. Talc mineralization in southwestern Montana is associated with hydrothermal alteration of Archean dolomitic marbles along faults in the southern margin of the middle Proterozoic Belt Seaway. Conditions of talc formation appear to have varied across the region and probably range from shallow hot spring systems to connate brine circulation pathways in Belt basin sediments. A road log description of the geology along a loop from Bozeman to Dillon, Montana, to visit both the Yellowstone and Regal talc mines accompanies this paper.

Google Earth Pro imagery was used by graduate students for a course project to identify, describe, and interpret lineament patterns on two oil-producing anticlines in Wyoming, one in the northwest Wind River Basin and the other in the southern Bighorn Basin (Maverick Springs and Thermopolis anticlines, respectively). These anticlines lie on opposite sides of the east-west–trending Owl Creek arch, which is a sinistral, transpressive array of en echelon, basement-involved thrust blocks. Both anticlines are well-exposed and display extensive near-surface fracturing and faulting, making them ideal candidates for a study of fold-related lineament patterns. Google Earth Pro was used to map and measure the orientation of lineaments and faults in a digital format. The lineaments identified include a set parallel to dip (A–C), a set parallel to strike (B–C), and two sets oblique to strike. Lineament orientation data were analyzed using length-weighted rose diagrams, whereas fold geometry and plunge were evaluated using equal-area (lower hemisphere) stereonets. Although the study was limited in scope to a computer-based geometric analysis and did not include outcrop-based kinematic data, the lineament/fracture data derived from Google Earth mapping are nevertheless compatible with published studies that demonstrate regional NE-SW shortening along the western Owl Creek transpressive zone during the Laramide orogeny. Google Earth Pro proved to be a highly effective tool for gathering lineament orientation and spatial distribution data across these well-exposed anticlines.