#gem otd

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Okenite

Photo Credit: Charles Creekmur

Okenite

WARNING: Many colourful specimens of Okenite, said to be from China or India, are currently available for sale. These are fake, the bright c

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Cortesognoite

Photo Credit: Cristophe Boutry

Cortesognoite

The V analogue of lawsonite.

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Veszelyite

Photo Credit: tak_collection

Veszelyite

The P analogue of arsenoveszelyite. A rare secondary Cu-Zn mineral occurring in the oxidised zones of base metal deposits.

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Rutile

Photo Credit: José Zendrera

Rutile

The most common member of the Rutile Group. Rutile is one of the five forms of titanium dioxide, TiO2, found in nature. Sellaite (magnes

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Labradorite

Photo Credit: JR Montgomery

Labradorite

A plagioclase feldspar with an albite : anorthite molar ratio ranging from 30 : 70 to 50 : 50. An intermediate member of the Albite-Anorthi

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Lileyite

Photo Credit: Marko Burkhardt

Lileyite

Visually indistinguishable from schüllerite.

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Eucryptite

Photo Credit: Simone Conti

Eucryptite

Phenakite Group.

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Euchlorine

Photo Credit: Jason B. Smith

Euchlorine

May form a group: "euchlorine group"; in this group the unit cell parameter a is very sensitive to the Na/K ratio. Structurally related t