Quartz (variety of colors)

Hardness: 7 (Mohs scale); Color: The beads display a range of colors including colorless (rock crystal), purple (amethyst), yellow/orange (citrine), pink (rose quartz), milky white, and possibly blue-grey (aquamarine or blue quartz). Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal system). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Quartz forms in a wide variety of geological environments. It can crystallize directly from magma in igneous rocks (like granite and pegmatite), deposit from hydrothermal fluids, or form in sedimentary rocks (like sandstone and chert) through processes of precipitation and recrystallization. The different color varieties are due to trace impurities or structural defects in the SiO2 lattice. For instance, amethyst's purple color comes from iron impurities and natural irradiation, while citrine's yellow/orange is often due to iron impurities, sometimes formed by heating amethyst. Rose quartz gets its pink hue from microscopic inclusions of dumortierite or other minerals. Geological Age: Quartz can be found in rocks of all ages, from Precambrian to Cenozoic.

Quartz, in its many forms, is widely used. Colorless quartz (rock crystal) and various colored varieties like amethyst, citrine, and rose quartz are popular as gemstones in jewelry. Industrial uses include electronic components (oscillators, filters), optical devices, abrasives, and as a component in glass, ceramics, and cement manufacturing. Sandstone, largely composed of quartz, is a major building material.

Quartz is the second most abundant mineral in Earth's continental crust, making up about 12% by volume. Its piezoelectric properties (generating an electric charge when mechanically stressed or vice-versa) make it crucial for modern electronics, particularly in watches, radios, and computers. The ancient Greeks believed clear quartz was perpetually frozen ice, hence the name 'krystallos'.

In the field, quartz is identified by its high hardness (it can scratch glass and steel), its characteristic glassy luster, and conchoidal fracture (shell-like breaks). It often forms distinct hexagonal crystals, though it can also be massive or granular. The specific color can help identify the variety. Given the diverse range of colors in the beads shown, it's a collection of various quartz types. Quartz is found globally in almost every country, especially in igneous, metamorphic, and sedimentary rocks. For collectors, well-formed crystals and intensely colored varieties are highly prized. The beads in the image, showing various colors and carvings, are likely polished and carved pieces of different quartz varieties.