Grossular

Grossular is a commonly 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 Ca3Al2 [ SiO4 ] 3, ie in chemical terms, a calcium aluminum silicate island.

Grossular usually develops dodecahedral or trapezoedrische crystals, but also granular to massive mineral aggregates. In pure form, the mineral is colorless and transparent. But since he on the one hand with andradite and Uvarovite forms a complete solid solution series and on the other hand contain various foreign admixtures, it usually occurs in different colors, but where prevails a yellow-green to dark green color, which has the grossular introduced its name. In addition, however, there are also golden yellow, pink to red, orange and yellowish brown to reddish brown Grossularite, some of which have received various proper names.

Etymology and history

It was named in 1811 by Abraham Gottlob Werner grossular, who named the mineral because of its green color often after the Latin word for gooseberry ( ribes grossularia ).

As a type locality applies Tschernyschewsk ( Chernyshevsk ) in Wiljui Basin in the Far Eastern Republic of Sakha (Yakutia ).

Classification

Already in the now outdated, but partly still in use 8th edition of the mineral classification by Strunz was one of grossular to mineral class of " silicates and Germanates " and then to the Department of " island silicates ( nesosilicates ) ", where he, together with andradite, Goldmanit and Uvarovite independent " garnet - Ugrandit series" 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 Grossular also included in the category of " silicates and Germanates " and then in the Department of the " island silicates ( nesosilicates ) ". This division, however, 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 and its construction in the subdivision of " island silicates without other anions; Cations can be found in oktahedraler and usually greater coordination, " where, along with almandine, andradite, Blythit, Calderit, Goldmanit, Henritermierit, Hibschite, Holtstamit, Hydroandradit, katoite, Kimzeyit, Knorringit, majorite, Morimotoit, pyrope, Schorlomit, Spessartin Skiagit, Uwarovit 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 grossular in the class of " silicates and Germanates " and then in the Department of the " island of silicate minerals " one. Here he is with andradite, Goldmanit, Uwarovit and Yamatoit in the " garnet group ( Ugrandit series) " with the system no. Find: " SiO4 groups with cations and > coordination island silicates " 51.04.03b within the subdivision.

Modifications and varieties

From grossularite several varieties are known:

• Hessonite: By admixtures of Fe3 ions to hyazinthrot orange colored grossular. An outdated and no longer common name for the Hessonite or cinnamon stone was Kaneelstein ( by Abraham Gottlob Werner). René -Just Haiiy named the variety after the Greek word Hesson for less, based on its in contrast to the "real" Hyacinth ( Zirkonvarietät ) lower value.
• Leukogranat ( from Ancient Greek λευκός leukos " white ") is the colorless variant of grossular.
• The emerald green tsavorite or tsavolite was not discovered until 1974.

Education and Locations

Grossular often forms in contact and regionalmetamorphen, calcium- rich rocks such as skarn or Rodingite, but may also by hydrothermal processes on clefts of these rocks occur as well in marly Kalksilikathornfelsen and occasionally in schists and serpentinites.

Accompanying minerals include calcite, Clinozoisit, diopside, dolomite, epidote, quartz, scapolite, tremolite, vesuvianite and wollastonite. Especially with vesuvianite, where the grossular often looks very similar, it can be easily confused due to the close paragenesis.

As a relatively common mineral formation Grossular has already been demonstrated in many localities, of which so far (as of 2011) are considered to be known around 1,200 localities.

In Germany the mineral previously occurred at several localities in the Black Forest in Baden- Württemberg, in many localities in Bavaria ( Franconia, Upper and Lower Bavaria ), in Hirzenhain and several discovery locations in the Odenwald in Hesse, near Bad Harzburg and Saint Andreas mountain in Lower Saxony, to many places in the Eifel, in Rammelsbach and Wolfenstein in Rhineland -Palatinate, in the Erzgebirge and Vogtland in Saxony, in several places in Schleswig -Holstein and in Unterbreizbach in Thuringia.

In Austria, grossular found primarily in Carinthia, Salzburg and Styria. In addition, he also showed off Kanitzriegel at Bernstein im Burgenland; at Schwallenbach, on Arzberg and the Siebenhandl quarry at Felbring ( Khajuraho am Jauerling ) in Lower Austria; at several points in the Fund Hinterbichler Dorfertal and im Zillertal in Tyrol; be detected in the Upper Austrian town Aigen in Mühlkreisautobahn and on the cleaning chamber Alp in the Verwallgruppe in Vorarlberg.

In Switzerland, the mineral, among others in the circle Bergell and Vorderrheintal in Graubünden, in the Matter and Saas Valley in the Valais and in Santa Maria di Claro ( Claro TI) was found in the canton of Ticino.

Other localities lie include Afghanistan, Egypt, Antarctica, Argentina, Australia, Brazil, Bulgaria, China, Ecuador, Finland, France, Greece, Greenland, Guinea, Honduras, India, Iraq, Iran, Ireland, Israel, Italy, Jamaica, Japan, Cambodia, Canada, Kenya, Colombia, Korea, Madagascar, Mali, Morocco, Mexico, Mongolia, Namibia, New Zealand, Norway, Pakistan, Peru, Poland, Portugal, Romania, Russia, Saudi Arabia, Slovakia, Spain, Sri Lanka, Sweden, South Africa, Taiwan, Tanzania, the Czech Republic, Turkey, Ukraine, Hungary, the U.S. Virgin Islands, the United Kingdom ( UK) and the United States of America (USA).

Crystal structure

Grossular crystallizes in the space group Ia3d cubic ( Raumgruppen-Nr. 230 ) with the lattice parameters a = 11.87 Å, and eight formula units per unit cell.

Use

Grossularite are like many other grenade valued and valuable gemstones that are processed depending on the quality either in different facets or cuts to Cabochonen.