Milky Quartz

Milky Quartz is the cloudy white to opaque variety of quartz (SiO2), its color caused by dense clouds of microscopic fluid and gas inclusions trapped during crystallization, which scatter light and give the crystal its characteristic greasy-to-vitreous luster. With a hardness of 7 and specific gravity of 2.65, it forms in an unusually wide range of environments: hydrothermal veins, granitic pegmatites, Alpine-type fissures, and even sedimentary limestone cavities. Because inclusions disrupt orderly growth, milky quartz crystals are frequently twinned, distorted, or double-terminated, and some growth forms — such as artichoke quartz and candle quartz — are almost always milky rather than clear.

Type localities and classic occurrences read like a world tour of mineralogy. In Germany's Sauerland, the famous Suttrop-type quartz (from Suttrop, near Warstein, and neighboring sites like Hohenlimburg-Oege) produces distinctive pseudohexagonal, double-terminated "Suttroper Diamanten" grown in Devonian limestone. In the Italian and French Alps, milky quartz from the Val Ferret and the Mont Blanc massif often shows a banded, marble-like pattern nicknamed marble quartz, while Sardinia's Mina Tini in the Iglesiente district yields small prismatic crystals capped with iron oxides. Portugal's Assunção Mine near Viseu and Norway's Blefjell are noted for milky candle and artichoke quartz habits, and in the United States, the Ground Hog Mine in Grant County, New Mexico, the Ohio Mine at Ouray, Colorado, and the pegmatite fields of Arkansas, Maine, and North Carolina all produce prized milky quartz clusters, some historically exceeding 35 cm. Brazil and Madagascar remain major modern sources of large decorative pieces.

Collectors seek milky quartz for its sculptural crystal habits, its role as a host for spectacular associated species — gold, rhodochrosite, fluorite, galena, pyrite, chalcopyrite, elbaite, and micas frequently occur on or within it — and for phantom growths where an early milky phase is enveloped by later clear quartz. Prospectors have long treated outcropping veins of milky quartz as an indicator of gold-bearing hydrothermal systems, adding a rich historical and economic dimension to specimens beyond their purely aesthetic and scientific appeal.