Peretaite
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| Peretaite | |
|---|---|
| General | |
| Category | Sulfate |
| Formula (repeating unit) | Ca(SbO)2(SO4)2(OH)2 · 2H2O |
| IMA symbol | Pta[1] |
| Crystal system | Monoclinic |
| Identification | |
| Color | Colorless, can be pink |
| Crystal habit | Prismatic crystals |
| Twinning | Very common on {100} |
| Cleavage | Perfect on {100} |
| Mohs scale hardness | 3.5-4 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 4.06 |
| Density | 3.8 g/cm3 |
| Optical properties | biaxial positive |
| Refractive index | nα= 1.686 nβ= 1.694 nγ= 1.709 |
| Pleochroism | Strong with colors pink(γ') to green(α') |
| Ultraviolet fluorescence | No |
| References | [2] |
Peretaite is a sulfate of antimony and calcium. 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, Tuscany, Italy.
Occurrence[edit]
Peretaite occurs in only small quantities, as aggregates of tabular crystals. The crystals are found in the geodes of a deeply silicified limestone. It also occurs in the cavities of columnar stibnite. Other associated minerals are stibnite, quartz, calcite, pyrite, valentinite, kermesite, sulfur, and gypsum.[2] 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[edit]
The mineral peretaite has transparent crystals that are colorless. It has a vitreous luster and perfect {100} 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.[2]
Chemical properties[edit]
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.[2] 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.[2]
| Oxide | Ideal weight percentage | Analytical Results |
|---|---|---|
| Sb2O3 | 68.31 | 69.09 |
| CaO | 6.58 | 6.44 |
| SO3 | 18.78 | 17.62 |
| H2O | 6.33 | 6.0 |
Crystallography[edit]
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[edit]
- List of minerals recognized by the International Mineralogical Association
- Classification of non-silicate minerals
References[edit]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c d e Nicola Cipriani, Silvio Menchetti, Paola Orlandi, Cesare Sabelli, 1980, "Peretaite a new mineral from Pereta, Tuscany, Italy", American Mineralogist, vol 65, pg 936-946.