A small amount of turquoise has been mined from several localities a few miles northwest of Sierra Blanca in the Sierra Blanca Mountains of Hudspeth County. GLOSSARY Amorphous—without definite molecular structure; not crystalline. Baroque stone—an irregularly shaped, polished stone; usually applied to tumbled stones. Baroque pearl—an irregularly shaped pearl. Brilliancy—reflecting much light; having brightness. Brilliant cut—a mode of arrangement of facets commonly used on round or oval stones. The standard American brilliant cut has 57 or 58 facets. Most diamonds of 5 or less carats are cut in this manner. Cabochon—a stone cut with a flat or convex upper surface; sometimes faceted in part. Opal, star sapphire, and agate are stones that are frequently cut in this style (fig. 2). Cambrian—a division of geologic time, estimated to be the time from 550 to 440 million years ago; the oldest time division of the Paleozoic era. Carat—a unit of weight equal to ⅕ of a gram or 0.2 gram. One ounce avoirdupois is equal to 141.75 carats. Cleavage—the tendency of certain minerals to split in particular directions yielding relatively smooth plane surfaces. Conchiolin—an organic albuminoid substance found in pearls. Conchoidal—a type of fracture having curved concavities or the approximate shape of one-half of a bivalve shell. Glass has excellent conchoidal fracture. Cretaceous—a division of geologic time, estimated to be the time from 135 to 60 million years ago; youngest division of the Mesozoic era. Crown—that portion of a faceted gem above the girdle; the upper portion of a facet-cut gem (fig. 6). Cryptocrystalline—composed of very fine or microscopic crystals. Crystal—the regular polyhedral form, bounded by plane surfaces, that is assumed by a mineral under suitable conditions. Crystals have definite external symmetry and internal molecular order. Crystalline—possessing definite internal molecular order; not amorphous. Cubic—in the general shape of a cube. The isometric crystal system is often called the cubic system. Culet—the very bottom portion of a faceted gem; the point or line formed by the intersection of the lowest pavilion facets (fig. 6). Dendritic—branching or tree-like in form. Diaphaneity—relative transparency. The diaphaneity of a mineral is described as transparent, translucent, opaque, etc. Dike—a tabular rock body, usually igneous in origin, which cuts across the surrounding rock strata. Dispersion—a measure of the ability of gemstones to separate complex or white light into its component colors; often illustrated with a prism. Gemstones that are capable of separating colors