Peretaite is a sulfate of

antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...

and

calcium Calcium is a chemical element; it has 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 to it ...

. The mineral, Ca(SbO)₄(SO₄)₂(OH)₂ (2(H₂O)), 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 Tuscany ( ; ) is a Regions of Italy, region in central Italy with an area of about and a population of 3,660,834 inhabitants as of 2025. The capital city is Florence. Tuscany is known for its landscapes, history, artistic legacy, and its in ...

, Italy.

Occurrence

Peretaite occurs in only small quantities, as aggregates of tabular crystals. The crystals are found in the

geode A geode (; ) is a geology, geological secondary formation within sedimentary rock, sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical rocks, in which masses of mineral matter (which may include crystals) are secluded. The crys ...

s of a deeply silicified

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

. It also occurs in the cavities of columnar

stibnite Stibnite, sometimes called antimonite, is a sulfide mineral, a mineral form of antimony trisulfide ( Sb2 S3). It is a soft, metallic grey crystalline solid with an orthorhombic space group. It is the most important source for the metalloid an ...

. Other associated minerals are stibnite,

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

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 ...

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 ...

valentinite Valentinite is an Antimony trioxide, antimony oxide mineral with formula antimony, Sb2oxygen, O3. Valentinite crystallizes in the orthorhombic system and typically forms as radiating clusters of euhedral crystals or as fibrous masses. It is colorl ...

kermesite Kermesite or antimony oxysulfide is also known as red antimony or ''purpur blende'' (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 ...

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

, and

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 ...

. 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.

References

{{Reflist Antimony minerals Calcium minerals Sulfate minerals

Occurrence

Physical properties

Chemical properties

Crystallography

See also

References