Cricket Mountains Mining District, Millard County, Utah, USAi

Regional Level Types
Cricket Mountains Mining District	Mining District
Millard County	County
Utah	State
USA	Country

The Cricket Mountains are in south-central Millard County, about 40 mi southwest of Delta. The mining district is a minor Pb-Ag producer and total recorded production for the area is just 60 tons of ore containing 17,000 pounds of Pb and 76 ounces of Ag. Total district metal production at modern metal prices is estimated at $18,000. The Rogers mine is the largest producer.
The Cricket Mountains are a north-northeasterly trending range in the Basin and Range Province of west-central Utah. Geologically, the range is primarily a moderately east-dipping (~25°) homoclinal sequence of Cambrian quartzites and carbonates. The weak Pb-Ag mineralization is hosted in the Middle Cambrian Howell Limestone. The ore consists of irregular blebs, replacements and stringers of galena in recrystallized massive limestone. Generally, fine- to medium-grained galena occurs as narrow hairline zones, veinlets, and in white, vuggy calcite veinlets. The ore is confined to moderately to strongly Fe-stained, massive limestone along minor fractures or narrow breccia zones that strike N. 50° E. and dip 70° NW. These mineralized structures do not parallel the main fault zones but are at angles of 30° to 50° to them and may represent tensional fractures. The in-place ore may contain as much as 8% to 10% galena, but mining usually produces much lower grades (Hintze, 1984). There are no intrusive igneous rocks recognized in the district and the ores do not have the high Ag:Pb ratio typical of intrusive-related ores.
Ferruginous quartzite is exposed as thin, discontinuous, horizons traceable for 2 to over 13 mi. These ferruginous beds occur in the quartzitic lower member of the Lower Cambrian Pioche Formation about 160 ft above the base (Hintze, 1984). Bullock (1970) reported that the ferruginous quartzite varies from 5 to more than 25 ft thick with an average thickness of about 18 ft, but Hintze (1984) reports thicknesses of only 3 to 6 ft for the most strongly hematitic portions. The ferruginous quartzite consists of fine- to coarse-grained, detrital quartz with hematite as grain coatings and void fillings. Thin-bedded quartzite is richer in Fe and contains more hematite as cement and as thin layers than the thicker bedded, more massive quartzite. The ores typically average about 20% Fe as hematite (Bullock, 1970).