#stellerite

Stellerite

Kazakhstan, Sokolovskoye field

Vanilla ice cream, mineral style

One of the large family of minerals known as zeolites, like the rest of them Stellerite tends to form in the bubbles, cracks and cavities in frozen low silica lava flows such as basalt as the hydrothermal convection cells powered by the still hot rocks redistribute varied elements, leaching and concentrating them before precipitating minerals as they cool or when chemical conditions change. It also forms during retrograde metamorphism. During the prograde version minerals change in response to increasing heat and pressure, while in the reverse path they turn back into lower P/T configurations, often in veins where fluids have redistributed elements. The name comes from its discoverer, an18th century CE German explorer and zoologist who also has a sea cow named after him. It is one of the less common members of the family, and unlike many doesn't have any industrial applications. Colour varies from white through pink to orange, with the latter usually being pale. The mineral is very similar to another zeolite called Stilbite (see https://bit.ly/2fbCj7n) and the two often occur together. With a Mohs hardness of 4 the mineral is not often faceted for collectors,

Its most common habit is as spheres and fans of radiating needle shaped crystals though single crystals are also found on occasion. There are several island locations in the Bering Sea where it is found (Copper island in the Komandorskiye archipelago being the type locality, occurring in a brecciated basalt, see https://bit.ly/2KuVdCr), as well a locale in the Chita region of Siberia. Other places include varied places in the USA, around Gunnedah in northern New South Wales, Sardinia and of course in the vast outpourings of lava that affected India at the close of the Mesozoic known as the Deccan Trapps, particularly at Jalgaon near Poona in Maharashtra whence came the lovely 17.3 x 15.5 x 10.0 cm specimen in the photo.

Loz

Image credit: Joe Budd /Rob Lavinsky/iRocks.com

@scrabdoodle Day 2 Gemsona Challenge: Stellerite

Stellerite

Kazakhstan, Sokolovskoye field