botryogen
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Botryogen is a hydrous
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
sulfate mineral The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary mine ...
with formula: MgFe3+(SO4)2(OH)·7H2O. It is also known as ''quetenite''. It crystallizes in the
monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...
prismatic system and typically occurs as vitreous bright yellow to red
botryoidal A botryoidal ( ) texture or mineral habit, is one in which the mineral has an external form composed of many rounded segments, named for the Ancient Greek (), meaning "a bunch of grapes".Adjective form: ''botruoeidēs'' This is a common form fo ...
to reniform masses and radiating crystal prisms. It has a
specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...
in the range 2 to 2.1 and
Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...
in the range of 2 to 2.5. It occurs in arid climates as a secondary alteration product of
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
-bearing deposits.Mineral Data Publishing - botryogen.pdf
/ref> It was first described in 1828 for an occurrence in the Falu mine of Falun, Dalarna,
Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
. It was named for its grape like appearance from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
''botrys'' for "bunch of grapes" and ''genos'' meaning "to bear".


References


Further reading

* Palache, C., H. Berman, and C. Frondel (1951) ''Dana’s system of mineralogy'', (7th edition), v. II, pp. 617–618. Sulfate minerals Monoclinic minerals Minerals in space group 14 {{sulfate-mineral-stub