Mineral name:  Fluorite Chemical formula:  CaF2 Location:  Eagle Mountains, Hudspeth County, Texas Crystal system and class:  Isometric  4/m32/m Genesis:  Fluorite is a common hydrothermal vein mineral, either as the major mineral or as a gangue (valueless) mineral with metallic ores.  It is especially common with lead and silver ores, where it occurs with a large number of other minerals including calcite, dolomite, gypsum, celestite, barite, quartz, galena, and sphalerite. This banded, multicolored fluorite precipitated from hydrothermal veins related to the explosive eruption of rhyolitic tuffs and dikes.  The Eagle Mountain fluorite was mined for use in the production of the element fluorine, which was needed by the Allies during World War II.  Quartz, calcite, and limonite occur with fluorite in some but not all of the hydrothermal veins in the Eagle Mountains.  Fluorite also commonly crystallizes in dolomites and limestones and occurs as a minor accessory minerals in some igneous rocks and pegmatites, together with cassiterite, topaz, tourmaline, and apatite.   Width x length of field of view in cm:  11 x 13 Specimen number:  E