Chiolite is a tetragonal-ditetragonal dipyramidal mineral, composed of sodium, fluorine, and aluminium. The name originates from the combination of the Greek words for snow (χιώυ) and stone (λίθος). It is an allusion to its similarity and appearance to
cryolite
Cryolite ( Na3 Al F6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987.
History
Cryolite was first described in 1798 by Danish vete ...
(ice stone). Chiolite is an
IMA approved mineral that has been grandfathered, meaning the name chiolite is believed to refer to a valid species to this day. Synonmys of chiolite are arksudite, arksutite, chodneffite, chodnewite and nipholith.
It was first discovered in the Ilmen mountains, Russia, in 1846.
Chiolite has been a valid species from the same year of its discovery.
Properties
Chiolite consists of fluorine (57.59% ), sodium (24.89%) and aluminium (17.53%). It does not show any radioactive properties whatsoever.
Twinning sometimes distorts the crystals into a prismatic shape.
In common literature, chiolite is usually referred to as having a 3.5 - 4 hardness on the mohs scale. However, chiolite is softer than cryolite is, which has a hardness of 2.5 - 3. Upon examining numerous samples, researchers determined chiolite to have a 2.5 hardness. When it is linked with topaz, brecciated chiolite transformed into cryolite among the fragments' rims according to a study. These transformations in thin sections appear to be solid state replacements. This transformation liberates both aluminium and potassium. With silica added, a reaction started with chiolite's breakdown, which formed topaz and potassium-mica.
Occurrences and usage
It is a type locality in Russia, but otherwise it has occurrences in Greenland and Virginia. It occurs in granite pegmatites. At its type locality, chiolite is associated with cryolite,
topaz
Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al Si O( F, OH). It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can mak ...
,
fluorite
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.
The Mohs sca ...
,
thomsenolite,
cryolihionite,
phekanite,
pachnolite and
elpasolite.
Due to its rarity, the difficulties of cutting the mineral and the lack of interest towards it, chiolite is rarely ever cut into a gem, hence why less than two dozens of cut specimens are estimated to exist. Cut stones that are clean always weight 1-2 carats as bigger clean specimens suitable for cutting do not exist.
[https://www.gemsociety.org/article/chiolite-jewelry-and-gemstone-information/]
References
Minerals