Selenite can also form as long, prismatic crystals. These twinned crystals take particular shapes known as ‘swallowtail’ or ‘spearhead’. It is often found twinned: a crystal started to grow and the growth direction changed abruptly in a symmetrical manner. Selenite crystallises in the monoclinic system, commonly as tabular crystals with a rhombus shaped outline. These tend to form in dry and sandy conditions.Ī selenite crystal with a recognisable rhombus shape. Desert rose refers to clusters of gypsum forming radiating, circular crystals that look like the petals of roses. Alabaster is the fine-grained, opaque form of gypsum appreciated for carving and ornamental use. Aside from the colourless crystals of selenite, other varieties include satin spar which is translucent, opalescent white with a fibrous structure. ![]() ![]() Gypsum is an hydrous calcium sulfate CaSO4♲H2O and an abundant mineral worldwide. He later applied his knowledge to agriculture and is regarded as a founding father of agricultural chemistry. His publication is the first one to present minerals systematically according to their chemical properties rather than their external appearance, which opened a new era in mineralogy. A professor of medicine and chemistry, he was also a mining specialist. Wallerius (1709-1785) in his 1747 book Mineralogia, eller Mineralriket. The original name was given to the mineral by the Swedish scientist J.G. Transparent to translucent with a glowing transparency, throughout history it has been compared to liquid light. The name alludes to the moon-like pale reflection the stone can give. Selenite was named after Selene the Greek goddess of the Moon, meaning literally the stone of the Moon (not to be confused with albite-orthoclase feldspar moonstone). Note also that selenite does not contain any selenium, and only shares the etymology of its name with that element. Assistant gemmology tutor, Dr Juliette Hibou FGA, explains more about the origins and properties of this striking gem material.Īlthough sometimes used as a synonymous for the mineral gypsum, selenite strictly refers to the colourless variety of gypsum. ![]() The Gem-A Gemstone & Mineral Collection contains this fantastic selenite specimen with grass-like green blades that shoot-out from the host rock.
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