Amethyst cluster

Translucent to transparent purple quartz crystals with a vitreous luster and six-sided prismatic crystal habit, commonly terminating in pyramidal points. Mohs hardness 7; no true cleavage, but conchoidal fracture; specific gravity about 2.65. The image has strong pink-purple and blue lighting, so the natural color may be less vivid than shown. Crystal faces and irregular fracture surfaces are visible.

Amethyst forms when silica-rich hydrothermal fluids or groundwater fill cavities and fractures in volcanic rocks, especially basalt, depositing quartz crystals. Trace iron is incorporated into the quartz and later irradiated to produce the purple color. Individual crystals may form over long periods, commonly in geologically young to ancient volcanic cavities; the exact age cannot be determined from the image.

Used as a gemstone, ornamental crystal, mineral specimen, and in jewelry. Large clusters and geodes are popular for display. Quartz is also important industrially in glass, ceramics, abrasives, electronics, and engineered stone, although attractive amethyst specimens are generally valued for collecting rather than industrial use.

Amethyst is the purple variety of quartz and is the February birthstone. Heating can turn some amethyst yellow, orange, or brown, producing citrine-like material. Excessive sunlight or heat may fade its color. The specimen appears to be a small crystal cluster rather than a cut gemstone.

Common sources include Brazil, Uruguay, Zambia, Namibia, Mexico, Bolivia, and the United States. In the field, identify amethyst by its purple color, glassy luster, hardness sufficient to scratch ordinary glass, lack of cleavage, and quartz crystal form. Distinguish it from fluorite, which is softer and has obvious cubic cleavage, and purple glass, which lacks natural crystal faces and has bubbles or flow textures. Image color is heavily stylized, so testing the physical specimen is needed for confidence.