Calderite

Calderit is a rarely occurring mineral from the group of garnets within the mineral class of " silicates and Germanates ". It crystallizes in the cubic crystal system with the idealized composition Mn3Fe23 [ SiO4 ] 3, is so chemically seen a manganese-iron silicate, which structurally belongs to the island silicates.

Since Calderit mixed crystals with Spessartine ( Mn3Al2 [ SiO4 ] 3) and andradite ( Ca3Fe2 [ SiO4 ] 3) and therefore usually small amounts of manganese by calcium and iron may be replaced diadoch by aluminum, is the chemical formula generally, even with ( Mn2 Ca ) 3 ( Fe 3 , Al) 2 [ SiO4 ] 3 below.

Calderit is transparent to translucent and developed only small, glass shiny crystals of orange-yellow, dark yellow, reddish -yellow or reddish-brown color. In thin layers, it can also be yellow to greenish yellow. In most cases, the mineral is found in the form of granular to massive mineral aggregates.

Etymology and history

Calderit 1909 was first scientifically described by Lewis Leigh Fermor ( 1880-1954 ), who named the mineral after the geologist James Calder to honor his work in relation to the geology of India.

The name Calderit was also used for a rock ( " Kut - Kumsany 12 miles northwest of Hazareebagh " ) and later for there occurring mineral. The Anglo-Indian scientist Henry Piddington first described the Calderit contained in rock samples of the rock. The samples stored for some time in the museum were previously only referred to as " undescribed Siliceo - Iron -and- Magnese rock, from the district of Burdwan ." The description of the mineral appeared in 1851 in an article Piddingtons in the "Journal of the Asiatic Society of Bengal" in which both Piddington and Calder were members of the "Asiatic Society of Bengal ."

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Calderit belonged to the department of " island silicates ( nesosilicates ) " where he, along with almandine, andradite, Goldmanit, grossular, Henritermierit, Hibschite, Holtstamit, Hydrougrandit, katoite Kimzeyit, Knorringit, majorite, Morimotoit, pyrope, Schorlomit, Spessartine, Uvarovite, wadalite, Yamatoit the " garnet " with the system no. VIII/A.08 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Calderit also in the department of " island silicates ( nesosilicates ) ". However, this is further subdivided according to the possible presence of other anions and the coordination of the cations involved, so that the mineral according to its composition in the subsection " island silicates without other anions; Cations can be found in oktahedraler and usually greater coordination, " where, along with almandine, andradite, Blythit, Goldmanit, grossular, Henritermierit, Hibschite, Holtstamit, Hydroandradit, katoite, Kimzeyit, Knorringit, majorite, Morimotoit, pyrope, Schorlomit, Spessartin Skiagit, Uvarovite and wadalite the " garnet " with the system no. 9.AD.25 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the Calderit in the department of " island silicate minerals ." Here he is with pyrope, almandine, spessartine, Knorringit and majorite in the " garnet group ( Pyralspit series) " with the system no. Find: " SiO4 groups with cations and > coordination island silicates " 51.04.03a within the subdivision.

Education and Locations

Calderit forms as a rare component in garnet solid solutions manganese-rich metamorphic and highly oxidized rocks. Accompanying minerals occur among others aegirine, Kutnohorit, hematite, pyrolusite, quartz, rhodonite and rhodochrosite.

A rare mineral formation Calderit has so far (as of 2012) are detected only at a few localities, of which approximately 10 localities as have been established. As the type locality Wabush iron formation applicable in Labrador in Canada and Otjosondu in the Namibian region Otjozondjupa. There are also the so far only known localities in these states.

In Europe, could the mineral including Italy ( Saint -Marcel (Aosta Valley ), Valtournenche ( valley ) ), Romania ( Iacobeni ( Sibiu) ), Sweden ( Pajsberg / Filipstad ) and Switzerland ( Ferreratal ) are found.

In addition Calderit occurred even at Katkamsandi ( Jharkhand ) and Netra ( Madhya Pradesh ) in India and in Aggeneys ( North Cape ) in South Africa.

Crystal structure

Calderit crystallizes in the space group Ia3d cubic ( Raumgruppen-Nr. 230 ) with the lattice parameters a = 11.82 Å, and eight formula units per unit cell.

Use

Pure Calderit kbar stable only at pressures above 30. However, its share increases with increasing pressures in the resulting garnet solid solutions continuously, so he is well suited as Geobarometer.