from a private collection in Liguria

Typically found in granitic pegmatites in Brazil (Minas Gerais), Pakistan, and Madagascar, it is an association of quartz crystals and silvery lamellae of muscovite, an aluminum-potassium mica. Both minerals crystallize during the slow cooling of granitic pegmatites, with muscovite forming through late magmatic crystallization or pneumatolytic metasomatism, while quartz precipitates later, filling the interstices or growing over the already formed mica lamellae. Hardness: 7 on the Mohs scale (quartz) and 2–2.5 on the Mohs scale (muscovite, which is much softer and cleaves into thin, elastic sheets).

This specimen is prized by collectors for the contrast between the transparency of the quartz and the silvery, silky luster of the muscovite; it is of educational interest for illustrating the sequence of pegmatitic crystallization; muscovite also has industrial applications as an electrical and thermal insulator.