Selenite (mineral) was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs 55 tons, is long, and is over 500,000 years old. Gypsum occurs on every continent and is the most common of all the sulfate minerals. Gypsum is formed as an evaporative mineral, frequently found in alkaline lake muds, clay beds, evaporated seas, salt flats, salt springs, and caves. It is frequently found in conjunction with other minerals such as, copper ores, sulfur and sulfides, silver, iron ores, coal, calcite, dolomite, limestone, and opal. Gypsum has been dated to almost every geologic age since the
Mineral each of which is distinguished from the others by unique chemical and physical properties. For example, quartz is defined by its formula, SiO, and a specific crystalline structure that distinguishes it from other minerals with the same chemical formula (termed polymorphs). When there exists a range of composition between two minerals species, a mineral series is defined. For example, the biotite series is represented by variable amounts of the endmembers phlogopite, siderophyllite, annite, and eastonite. In contrast, a mineral group is a grouping of mineral species with some common chemical properties that share a crystal structure. The pyroxene group has