Abstract

The Pearl Queen mine of the Basin Perlite Company is located about 10 miles northeast of Milford in Beaver County, Utah. The perlite deposit was first recognized in 1948 and has a long and varied history of exploration and mining. It is estimated that about 28.5 million tons of perlite resources are present on the mine property.

The mine is located on the western flank of the Mineral Mountains, which are an uplifted north-trending fault block composed primarily of multiple-phase Tertiary plutons and volcanic rhyolite flows. The perlite resources occur as a blanket up to 90 feet thick at the top of the Bailey Ridge flow and are thought to have been formed by low temperature hydration of obsidian.

Perlite is an aluminosilicate rock containing about 74 percent amorphous SiO₂, 12 percent Al₂O₃, 3 percent Na₂O, 4 percent K₂O and other minor constituents. About 3 percent “combined” water occurs as microscopic droplets which vaporize when heated and cause the rock to “pop”, forming light-weight perlite products.

The mine is a typical surface mining operation. Crushed rock is hauled to the Milford plant, which can produce about 100,000 tons of sized perlite products per year. These products are shipped to various customers throughout the United States. Fine-ground perlite rock is also thermally expanded to produce a value-added product called microspheres. Microspheres are a very light-weight material that is used as a specialty filler by the construction industry.