Peretaite is a sulfate of
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient t ...
and
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
. The mineral, Ca(SbO)
4(SO
4)
2(OH)
2
(2(H
2O)), was named Peretaite for its locality. It was first discovered in an antimony-bearing vein at
Pereta
Pereta is a village in Tuscany, central Italy, administratively a frazione of the comune of Magliano in Toscana, province of Grosseto, in the area of Maremma. At the time of the 2001 census its population amounted to 182.Tuscany
it, Toscano (man) it, Toscana (woman)
, population_note =
, population_blank1_title =
, population_blank1 =
, demographics_type1 = Citizenship
, demographics1_footnotes =
, demographics1_title1 = Italian
, demogra ...
, Italy.
Occurrence
Peretaite occurs in only small quantities, as aggregates of
tabular crystals. The crystals are found in the
geode
A geode (; ) is a geological secondary formation within sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical rocks, in which masses of mineral matter (which may include crystals) are secluded. The crystals are formed by the fill ...
s of a deeply silicified
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
. It also occurs in the cavities of columnar
stibnite
Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb2 S3. This soft grey material crystallizes in an orthorhombic space group. It is the most important source for the metalloid antimony. The name is derived from the ...
. Other associated minerals are stibnite,
quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
,
calcite,
pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic luster and pale brass-yellow hue giv ...
,
valentinite
Valentinite is an antimony oxide mineral with formula Sb2 O3. Valentinite crystallizes in the orthorhombic system and typically forms as radiating clusters of euhedral crystals or as fibrous masses. It is colorless to white with occasional shad ...
,
kermesite
Kermesite or antimony oxysulfide is also known as red antimony (Sb2S2O) . The mineral's color ranges from cherry red to a dark red to a black. Kermesite is the result of partial oxidation between stibnite (Sb2S3) and other antimony oxides such a ...
,
sulfur, and
gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate 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, blackboard or sidewalk chalk, and drywal ...
.
[ Peretaite can often be red from the inclusion of valentinite. The mineral was formed by the action of sulfuric acid on the stibnite; peretaite is closer to the boundary of the country rock limestone, which is the source of the calcium in peretaite.
]
Physical properties
The mineral peretaite has transparent crystals that are colorless. It has a vitreous luster and perfect cleavage. The density of peretaite was determined by a heavy-liquid method, crystals tend to float in a Clerici solution, which has a density of 4.0 g/cm3, therefore the density is 3.8 g/cm3.[
]
Chemical properties
The mineral is made up of 4 oxides. Most of this mineral is made up of an Antimony oxide, Calcium, and a sulfur oxide. Some of the qualitative analyses of peretaite were done by an ORTEC X-ray microanalyzer and an ARL SEMQ electron microprobe.[ Later it was discovered that the crystals would disintegrate under the electron beam. Therefore, a wet chemical analysis was performed for the sulfur content, calcium was determined by atomic absorption, and antimony was determined by alternating current anodic stripping voltammetry.][
]
Crystallography
X-ray single-crystal study indicated peretaite had a symmetry of 2/m with a space group of C2/c or Cc and a crystal system of monoclinic.
See also
*
*Classification of non-silicate minerals
This list gives an overview of the classification of non-silicate minerals and includes mostly International Mineralogical Association (IMA) recognized minerals and its groupings. This list complements the List of minerals recognized by the Inter ...
References
{{Reflist
Antimony minerals
Calcium minerals
Sulfate minerals