Mineralienatlas (name for mineral atlas) is the platform for people interested in mineralogy, geology, palaeontology and mining since 2001. We operate a significant database for minerals, fossils, rocks and their localities. Mineralienatlas is not limited to a section. We bring together information and inform comprehensive.

To complete our information constantly, we need your support. With us, everyone can and should participate. Currently Mineralienatlas is used and expanded by 10586 members. Every month hundreds of thousands of visitors use our website as an information source.
 
Geolitho Foundation non-profit GmbH
Geolitho Foundation non-profit GmbH is the non-profit supporter of the Mineral Atlas (Mineralienatlas), the Lithotheque, the Geolitho Collection Management and the Marketplace and Store by collectors for collectors. The Foundation promotes public education in the field of mineralogy, geology, paleontology and mining by operating, maintaining and further expanding earth science projects.
 
https://www.chiemgauer-mineralien-fossiliensammler.de/
https://www.mineralbox.biz
https://www.edelsteine-neuburg.de
https://www.lithomania.de
hausen - Mineraliengrosshandel.com
https://www.juwelo.de
 
... Von den weltweit weni­gen Fun­dorten (darun­ter Brasilien, Sri Lan­ka und Zim­bab­we) sind die rus­sischen Alexan­drite die hoch­w­ertig­sten, da sie im Ge­gen­satz zu den meist weniger kräftig ge­färbten Stei­nen aus den an­deren Län­dern ihre Farbe von einem in­ten­siv­en smaragd­grün zu einem tie­fen pur­pur­rot wec ... more... Von den weltweit wenigen Fundorten (darunter Brasilien, Sri Lanka und Zimbabwe) sind die russischen Alexandrite die hochwertigsten, da sie im Gegensatz zu den meist weniger kräftig gefärbten Steinen aus den anderen Ländern ihre Farbe von einem intensiven smaragdgrün zu einem tiefen purpurrot wechseln. Die Originalfundstelle im Ural war nach mehreren Jahrzehnten Abbau erschöpft und nur wenige dieser berühmten Alexandrite tauchen ab und zu auf dem Markt auf. Neuere Funde stammen aus Zimbabwe, Sri Lanka, Tansania, Tasmanien, Indien und Myanmar (Burma), besitzen jedoch nicht den starken Farbwechsel der russischen Alexandrite. Im Jahr 1987 entdeckte man in Hematita (Minas Gerais) in Brasilien Alexandrite, welche nahe an die Qualität der historischen russischen Steine herankommen und einen attraktiven ... Ein Beitrag von Peter Seroka
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... As al­ready men­tioned else­where, min­ing in Il­me­nau dates back to the year 1200. In 1216, Count Pop­po v. Hen­ne­berg was en­fe­offed with the Ber­gre­gal by Frie­drich den II. At that time one had dis­cov­ered min­er­alised steep cop­per slate near Ro­da and on the Sturmheide. Pre­sum­ab­ly, in­di­vi­d­u­al min­ers had ... more... As already mentioned elsewhere, mining in Ilmenau dates back to the year 1200. In 1216, Count Poppo v. Henneberg was enfeoffed with the Bergregal by Friedrich den II. At that time one had discovered mineralised steep copper slate near Roda and on the Sturmheide. Presumably, individual miners had been enfeoffed, who extracted copper slate and sandstone in accordance with the mining freedom. This is generally regarded as the beginning of the first main period of Ilmenau mining. The ore was mined in small open pits to a maximum depth of 50m. ... A Contribution of {:10697:}
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Ara­g­onite is a cal­ci­um car­bo­nate, chem­i­cal­ly iden­ti­cal with calcite. The min­er­al calcite, how­ev­er, dif­fers from Ara­g­onite due to its in­ter­nal crys­tal struc­ture. While the crys­tal sys­tem of calcite is trig­o­n­al, the sys­tem of ara­g­onite is rhom­bic. Dense mass­es of small ara­g­onite crys­tals are dif­fi­cul ... moreAragonite is a calcium carbonate, chemically identical with calcite. The mineral calcite, however, differs from Aragonite due to its internal crystal structure. While the crystal system of calcite is trigonal, the system of aragonite is rhombic. Dense masses of small aragonite crystals are difficult to distinguish from calcite, but they are larger, they show a distinct habit.

A lot of chapters in this portrait will give you much more details about this interesting mineral. Written and investigated by Peter Seroka. (Article in german)
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https://crystalparadise.de/
https://vfmg.de/der-aufschluss/
https://www.mineral-bosse.de
Mineralien Kalender
Edelsteintage Konstanz
https://fossilsworldwide.de/