Quartz (likely milky/rose quartz variety)

Hardness: 7 on the Mohs scale. Color: Often colorless, but can also be milky white, grey. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal). Cleavage: None. Fracture: Conchoidal (shell-like). Specific Gravity: 2.65.

Quartz typically forms in igneous, metamorphic, and sedimentary environments. In igneous rocks, it crystallizes from silicic magmas. In metamorphic rocks, it forms under conditions of high temperature and pressure. In sedimentary settings, quartz is a primary constituent of sandstones and cherts, often forming from the weathering of other rocks and subsequent cementation. Its formation can occur over vast geological ages.

Quartz has numerous uses. In industry, it's used as an abrasive, in electronics (due to its piezoelectric properties), in glass manufacturing, and as a component in ceramics. In construction, quartz sand is a key ingredient in concrete and mortar. Many varieties are highly valued as gemstones for jewelry and ornamental objects, such as amethyst and citrine.

Quartz is the most abundant mineral in the Earth's crust, making up about 12% by volume. It is highly resistant to weathering, which is why it's a common component of sands and sedimentary rocks. Many varieties of quartz exist, including amethyst, citrine, rose quartz, smoky quartz, and chalcedony, each valued for different reasons.

In the field, quartz can be identified by its hardness (it can scratch glass), its glassy luster, and its conchoidal fracture. Unlike many other minerals, it does not have cleavage. Its common presence in many rock types also aids in identification. It is found globally in almost every country. For collectors, well-formed crystals and colorful varieties like amethyst or rose quartz are highly sought after. Rounded, opaque specimens like the one pictured are very common as stream or beach pebbles, indicative of their durability.