Satin spar, less commonly atlas spar, is a
trivial, partly obsolete name for fibrous varieties of two minerals,
gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...
and
calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
,
[''Krivovichev V. G.'' Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)''] possessing a characteristic
silk
Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...
y (
satin
A satin weave is a type of Textile, fabric weave that produces a characteristically glossy, smooth or lustrous material, typically with a glossy top surface and a dull back; it is not durable, as it tends to snag. It is one of three fundamen ...
)
luster. Despite their very low hardness (2 or 3 on the
Mohs scale
The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material.
The scale was introduced in 1812 by the Ger ...
), both atlas (satin) spars (especially
selenite) are widely used as ornamental stones.
It should be understood that both of the listed minerals, despite their name of “
spars
SPARS was the authorized nickname for the United States Coast Guard (USCG) Women's Reserve. The nickname was derived from the USCG's motto, "—"Always Ready" (''SPAR''). The Women's Reserve was established by law in November 1942 during Wor ...
”, do not strictly belong to the number of the most well-known under this name ''
feldspar
Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...
s'' — both from the point of view of chemical composition and from the standpoint of classical
mineralogy
Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...
.
Main minerals and varieties
*
Selenite is a fibrous variety of
gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...
,
the most common form of satin spars;
*
Gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...
, ''satin spar''
in the form of a lustrous fibrous variety, not, however, defined as selenite;
[''R. A. Lidin, L. L. Andreeva, V. A. Molochko''. Constants of inorganic substances: handbook. 3rd ed., reprinted, edited by R. A. Lidin. — Москва: Дрофа, 2008 г. — 685 с. ''(in Russian)'']
*
Calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
or ''calcite spar'' is a fibrous variety
['' G. F. Herbert Smith''. Gemstones. 14th ed., reviewed by F. C. Phillips. — London, Chapman & Hall, 1972. — 580 p. ISBN 0412108909] superficially resembling selenite,
['' Boris Cantor''. Collecting Minerals. 2nd edition, revised and enlarged. — Moscow: Nedra, 1991. — 173 p. ''(in Russian)''] but much less common in nature;
*
Aragonite
Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...
is one of the polymorphic natural varieties of calcite,
sometimes having the same ''
satin
A satin weave is a type of Textile, fabric weave that produces a characteristically glossy, smooth or lustrous material, typically with a glossy top surface and a dull back; it is not durable, as it tends to snag. It is one of three fundamen ...
'' effect.
Satin Spars Gallery
Gypse, ankérite 90-1-0050.JPG,
Gypsum-261802.jpg,
002CalcitePER.jpg,
Aragonite-171607.jpg,
See also
*
Feldspar
Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...
s
*
Azure spar
Azure spar, sometimes azur-spar, is a trivial and commercial, partly obsolete name for several of the most famous bright blue or blue-colored minerals, which also have similar names, most notably for lazurite and azurite,''Krivovichev V. G.'' Mi ...
*
Moonstone
*
Belomorite
*
Albite
Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula . It is a tectosilicat ...
*
Tiger eye
References
{{Set index article
Set index articles on minerals
Calcium minerals
Carbonate minerals
Sulfate minerals
Mining terminology
Mineral groups