Lorenzenite
Lavas and magmas are distinguished according to the percentage of silica they contain, along with the percentages of other major and trace elements present in their constituents. The percentage of silica affects both the properties of the magma (more silica makes them more viscous for example, and the consequent eruptions more explosive) and what minerals form when it erupts and freezes as lava. In many cases there is plenty of silica to go round and the more common feldspars, pyroxenes, olivine or amphiboles form, but when the magma is undersaturated in silica (ie doesn’t have enough to combine with elements into separate silicates, say of sodium and titanium) then a distinct class of minerals, and lavas form.
This rare mineral is one of them, typically forming as grey, pink, mauve or brown prisms that only occur in a couple places on Earth, at least in any appreciable size. It was discovered in Greenland in 1897, and mineralogists later realised that it had been ‘discovered’ a second time in Russia’s Kola Peninsula (where it was christened Ramsayite, which is still used as a synonym at times). Its source rock is a granitoid rock crystallised from a magma that stalled on the way up called a nepheline syenite, filled with silica undersaturated minerals. It was named after a Danish mineralogist who was an expert on Greenland’s rocks. The 3.6 x 2.8 x 2 cm specimen on matrix was mined in Russia.
Loz
Image credit: Spirifer Minerals
https://www.mindat.org/min-2436.html
http://bit.ly/2yOdtBu
http://www.galleries.com/Lorenzenite
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