Selenite is the same as quartz

Selenite

Author: Torsten Purle (steine-und-minerale.de) | Last update: 23.03.2021


Selenite - properties, formation and use

english: selenite | French: sélénite



Selenite - gypsum in its purest form

The name selenite was first found in mineralogical literature in 1747. In his remarks on "Selenite - Spegelsten" the Swedish chemist and mineralogist Johan Gottschalk Wallerius (1709 to 1785) describes the mineral in detail under the heading "Gipsarter". However, at this point he does not give any clues as to what inspired him to give the name. The fact is that the meaning of the name Selenite comes from the Greek word for moon - selene - goes back what literally with Moonstone is translated.

As can be seen from other mineralogists of the time, the term mirror stone had been known for a long time. The paleontologist and archaeologist Johann Samuel Schröter (1735 to 1808) writes that selenite was called a mirror stone (Lunaris) by the ancient Romans, "Because the image of the moon can be reflected in it when it shines on it". The mineralogist Johann Friedrich Henkel noted in 1759 that the name "Of the moon-white color" of the mineral, i.e. the clear, white reflections that are reminiscent of the moon.

Properties of selenite

Selenite is a variety of gypsum with the chemical composition CaSO4· 2H2O, which is assigned to the sulphate class commonly used in mineralogy.
Referring to the "relationship" with gypsum and the tabular-spatulate crystals, selenite is referred to as gypsum spar, especially in the older literature, under the term in Wallerius gypsum lamellis.

Selenite is predominantly from white color or colorless. Various admixtures give the mineral delicate, clear colors.
When describing selenite from a gypsum quarry near Quedlingburg, Wallerius made a distinction between white, yellow and shimmering selenite (Selenites albus, Selenites flauus and Selenites versicolor).
The streak color of selenite - that is, the color that appears when a mineral is brushed over an unglazed porcelain board, is white.

Selenite crystallizes following the monoclinic crystal system. The crystals of selenite are prismatic and tabular or, as Wallerius already recognized: "consists of nothing but leaves and discs, so that a leaf, as thin as it is, can be divided into other slices". The aggregates are described as rosette-like, granular, bulky or fibrous.

Selenite is characterized by a fibrous, shell-like and splintering fracture, the cleavage is perfect. Selenite has a glass-like sheen, with a pearl-like to silk-like sheen on the cleavage surfaces. The transparency of the crystals is opaque to transparent.

Selenite has a Mohs hardness of 1.5 to 2 on the 10-point scale of the hardness of minerals according to the mineralogist Friedrich Mohs (1773 to 1839) very soft mineral. The density is 2.32 g / cm3.



Marienglas and selenite

The term Marienglas summarizes particularly clear selenite crystals that were used in the past for depictions of Mary or Mary and Jesus instead of glass.


Formation and distribution of selenite

As a mineral of sedimentary origin, selenite occurs mainly in the oxidation zone of sulfide-containing ore deposits or in salt domes.
The formation of selenite is also possible via the metamorphosis of anhydrite. Selenite is also partially integrated in clay stones or sands.

The occurrences of selenite are associated with zinc blende, pyrite and halite, galena and calcite, among other things.

You can find selenite, for example, in Friedrichroda (Marienglashöhle), Osterode, Staßfurt, Eisleben / Germany; Carinthia / Austria; Volterra / Italy; Poland; England; France; Russia; Utah, Dakota, Michigan, Kentucky, Kansas / USA; Mexico; Peru; Madagascar and Morocco.


Selenite - Our recommendation *


Uses and importance of selenite

Selenite was already used in ancient Rome. Crystal clear specimens were assembled to form windows or used as mirrors - hence the name mirror stone (Lapis specularis) as a synonym for Marienglas (Glacies Mariae).

Nowadays, selenite is used in the construction industry, for example as a binding agent, plaster of paris, which is given a fine sheen by selenite, or as a lightweight construction material.

As a gemstone, selenite is less important. The mineral is too soft and filigree to be suitable for processing into jewelry. Moonstones that are sold as gemstones are very likely not selenite, but the feldspar variety moonstone.

In addition, selenite is used as a healing stone, without the healing properties of selenite being able to be confirmed in clinical studies.


Evidence of selenite

If selenite is heated over the flame to over 163 ° C in an unsealed test tube, water is released. Selenite is almost insoluble in acids.


See also:
⇒ Desert roses - roses made of sand and plaster of paris
⇒ stone paper
⇒ alabaster


Swell:
⇒ Wallerius, J. G. (1747): Mineralogia, Eller Mineralriket, Indelt och beskrifvit
⇒ Wallerius, J. G. (1750): Johann Gottschalk Wallerius, The world wisdom and medical art doctor on the royal. Akademiez zu Upsala, the medical faculty Adiunctus, the Roman imperial academy of natural scientists, also of the royal. medical college in Stockholm member, Mineralogy, or mineral kingdom classified and described by Him. Berlin 1750
⇒ Schröter, J. S. (1784): Lithologisches Real- und Verballexikon. Stones and fossils. Sixth volume.
⇒ Henkel, J. F. (1759): Flora in mineralogia redivivus. From mineralogy or science. Of water, earth's juices, salts, earth, stones and ores
⇒ Pellant, C. (1994): Stones and Minerals. Ravensburger nature guide. Ravensburger Buchverlag Otto Maier GmbH
⇒ Bauer, J .; Tvrz, F. (1993): The Cosmos Mineral Guide. Minerals rocks precious stones. An identification book with 576 color photos. Gondrom Verlag GmbH Bindlach
⇒ Korbel, P .; Novak, M. and W. Horwath (2002): Mineralien Enzyklopädie, Dörfler Verlag
⇒ Medenbach, O .; Sussieck-Fornefeld, C .; Steinbach, G. (1996): Steinbach's natural guide minerals. 223 species descriptions, 362 color photos, 250 drawings and 30 pages of identification tables. Mosaik Verlag Munich
⇒ Schumann, W. (1991): Minerals rocks - characteristics, occurrence and use. FSVO nature guide. BLV Verlagsgesellschaft mbH Munich

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