Tridymite, Osumilite
Funtanafigu Quarry, Marrubiu, Oristano Province, Sardinia, Italy
5.7 x 4.3 x 3.2 cm. Tridymite is high-temperature quartz and osumilite is a rare complex silicate, both found in volcanic rocks. Tan tridymite crystals (rare at this well-known Sardinian locale) richly line a vug in rhyolite matrix and a rich band and isolated crystals of brown, lustrous, hexagonal, prisms and blades, to 3 mm, of osumilite are a ...
© Rob Lavinsky & irocks.com