Purpurite

• Manganipurpurit

Purpurit is a rarely occurring mineral from the mineral class " phosphates, arsenates and vanadates ." It crystallizes in the orthorhombic crystal system with the idealized composition Mn3 [ PO4 ], and is therefore chemically seen a manganese phosphate. Since Purpurit forms a complete solid solution series with heterosite ( Fe3 [ PO4 ] ) and is therefore always to be found in nature with a certain amount of iron in the compound, the formula of Purpurit is generally indicated with ( Mn3 , Fe3 ) PO4.

Purpurit is translucent to opaque and does not form visible crystals. Usually, he finds himself in the form of granular to massive aggregates up to 20 cm size from reddish violet to deep dark pink color with light violet to pale red line color. The surfaces of fresh samples usually have a silky shine. Over time, the color can go through weathering to a dark brown to brownish black, and the surfaces are matt.

The Mohs hardness of Purpurit is between 4 and 4.5. It is therefore usually a little harder than the reference mineral fluorite ( 4), but softer than apatite (5) and can therefore be a good knife also more scratch.

Etymology and history

Was first discovered Purpurit in the " Fair Mine" at Kings Mountain ( Gaston County) in the U.S. state of North Carolina and described in 1905 by Louis Caryl Graton and Waldemar Theodore Schaller, who named the mineral based on its characteristic color from the Latin word purpura.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Purpurit belonged to the general ward of the " water clear phosphates without foreign anions ", where he along with Ferrisicklerit, heterosite, Lithiophilit, Marićit, Natrophilit, Sicklerit, Simferit and Triphylin untitled set VII/A.02 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Purpurit also in the department of " Phosphates, etc. without additional anions, without H2O" one. However, this is further divided according to the relative size of the cations involved, so that the mineral is found according to its composition in the subsection "With medium-sized cations " where it together with Ferrisicklerit, heterosite, Lithiophilit, Natrophilit, Sicklerit, Simferit and Triphylin " Triphylingruppe " with the system number. 8.AB.10 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the Purpurit in the class of " phosphates, arsenates and vanadates " and there in the department of " Anhydrous Phosphates, etc. " field. Here it is only together with heterosite in the unnamed group 38.04.01 within the sub-division of " water clear phosphates, etc., A XO4 " to find.

Education and Locations

Purpurit forms predominantly secondarily as encrusting forming oxidation product of Triphylin (LiFe [ PO3 ] ) or Lithiophilit ( LiMn [ PO3 ] ). Rarely, it can also occur primarily in the form of granular masses in granitic pegmatites. Accompanying minerals occur in different, mostly also secondary phosphate minerals such as Sicklerit.

A rare mineral formation Purpurit could be detected only a few localities. to be known (as of 2011) shall apply so far about 80 localities. Apart from its type locality " Fair Mine" came the mineral in the United States, among others, yet at several locations in Arizona, California, Colorado, Connecticut, Maine and South Dakota as well as in the co- located in North Carolina, " Foote Mine" ( Cleveland County) and in the " Animikie Red Ace " pegmatites in distance in Wisconsin.

In Germany Purpurit occurred so far in the pegmatite to in Zwiesel in the Bavarian Forest and Hagendorf ( Waidhaus ) in the Upper Palatinate Forest.

In Austria, found the mineral spodumene at a trial mining on fire back in Carinthia ( see also mining in Carinthia ).

Other localities lie including Australia, Brazil, China, Finland, France, Canada, Madagascar, Namibia, Portugal, Rwanda, Sweden, Spain, South Africa, Czech Republic.

Crystal structure

Purpurit crystallizes in the orthorhombic space group Pbnm ( Raumgruppen-Nr. 62) with the lattice parameters a = 4.78 Å; b = 9.77 Å and c = 5.82 Å and four formula units per unit cell.

Use as a gemstone

Purpurit is processed due to its low hardness rather rare gems, but then, occasionally ground mainly as a drum stone in cabochon.