Stellerite
Formula: Ca4(Si28Al8)O72 · 28H2O
Species: Silicates – (Tectosilicates)
Colour: Colourless to white, pink, orange
Lustre: Pearly
Hardness: 4½
Specific Gravity: 2.13
Crystal System: Orthorhombic
Member of: Stilbite Subgroup > Zeolite Group
Name: Named after Georg Wilhelm Steller (1709-1746), German explorer and zoologist.
Type Locality: Medny Island, Commander Islands (Komandorskie Islands), Kamchatka Krai – Russia
Easily confused with the chemically similar stilbite-Ca and other members of the stilbite subgroup. Bladed crystals may be confused with colourless prehnite. It is the orthorhombic, Ca-rich end member of a series consisting of stellerite, the monoclinic stilbite-Ca and stilbite-Na, plus the Na-dominant, orthorhombic barrerite. Stellerite can be found as individual crystals, as well as fan-, bow-tie-, sheaf-like and spherical aggregates that are also typical for stilbite-Ca. Although normally white, stellerite can be found in several other colors. The orange, pink and salmon colors often found in Garrawalla, Australia, are due to minute inclusions of hematite. Celadonite, or other clay inclusions, may give greenish grey colors. The most attractive crystals are found in cavities in basalt, but stellerite is also found in hydrothermal systems in a wide variety of host rocks, such as hornfels, granites, granitic gneiss, pegmatites, and amphibolites.