Whitlockite

Whitlockite is a rarely occurring mineral from the mineral class of " phosphates, arsenates and vanadates ." It crystallizes in the trigonal crystal system, with the chemical composition of CA9 (Mg, Fe) [ PO3OH | (PO4) 6] and usually develops tabular or rhombohedral crystals, but granular mineral aggregates and microcrystalline crusts. Also the formation of cave pearls is possible. Visible crystal faces have a glass or resinous luster, crusty formations, however, are rather dull.

Reiner whitlockite is colorless and transparent. However, it can appear white by multiple refraction due multicrystalline training or lattice defects and accept by foreign admixtures a gray or yellowish color, the transparency decreases accordingly. However, the stroke color is always white.

With a Mohs hardness of 5 Whitlockite belongs to the medium-hard minerals that can be similar to the reference mineral apatite carve with the knife still.

Special Features

The mineral is piezoelectric and pyroelectric, ie changes in periodic pressure or temperature changes its electrical polarization and thereby builds an electrical voltage.

Etymology and history

Was first discovered by Harold J. Whitlockite Verrow in the " Palermo No. 1 Mine " at Groton in Grafton County ( New Hampshire) in the United States (USA) and described in 1940 by Clifford Frondel, who named the mineral after Herbert Percy Whitlock ( 1868-1948 ), the curator of minerals and gems from the American Museum of Natural History.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Whitlockite belonged to the mineral class of " phosphates, arsenates and vanadates " and then to the Department of " water clear phosphates without foreign anions ", where he along with Brianit, Farringtonit, Panethit, Stanfieldit, Strontiowhitlockit Tuit and formed a distinct group.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Whitlockite also in the class of " phosphates, arsenates and vanadates " and there in the department of " phosphates, etc., without additional anions, without a H2O ". This division, however, is further divided according to the size of the cations involved, so that the mineral is found according to its composition in the subsection "With medium -sized and large cations " where there is a namesake of the " Whitlockitgruppe " with the system no. Forms 8.AC.45 and the other members Bobdownsit, Ferromerrillit, Merrillit, Strontiowhitlockit and Tuit.

The mainly common in English-speaking classification of minerals according to Dana assigns the whitlockite in the class of " phosphates, arsenates and vanadates " and there in the department of " Anhydrous Phosphates, etc. " field. He is also named as the " Whitlockitgruppe " with the system no. 38.03.04 and the other members Bobdownsit, Ferromerrillit, Merrillit, Merrillit (Ca ), Merrillit - (Y), and Strontiowhitlockit Tuit within the sub-division of " water clear phosphates, etc., (A B2 ) 3 ( XO4 ) 2 " to find.

Education and Locations

Whitlockite forms as a rare secondary mineral by hydrothermal processes of primary phosphates in granitic pegmatites, but rarely also in sediments such as phosphorites. Also in the form of cave pearls whitlockite can be found .. In Stone meteorites, especially in chondrites, whitlockite is (besides apatite ) regularly also in the silicate inclusions of the IAB iron meteorites country Whilockit was found. Furthermore whitlockite can entshehen on limestone by the action of liquid excrement of sea birds (eg penguins and cormorants ). It is part of the so forming guano.

Depending on the formation condition whitlockite may associated with different minerals occur, among other Ludlamit, Fairfieldit, Triphylin, siderite, apatite and quartz in pegmatites; with hydroxyapatite in hollows and Stanfieldit, Farringtonit and Brianit in meteorites.

Overall whitlockite has so far (as of 2011) are detected in 65 localities. Apart from its type locality " Palermo No. 1 Mine " at Groton entered the mineral in the USA nor in Hyampom in Trinity County ( California ); Woodbine meteorite in Jo Daviess County ( Illinois); in Poland, Newry and Rumford (Maine) in Maine; the "Gold Strike Mine" at Lynn (Eureka County) and the "Twin Creeks Mine" at Potosi ( Humboldt County) in Nevada; on Parker Mountain in Strafford County ( New Hampshire); Near Custer (South Dakota); in the Crawford Mountains in Rich County ( Utah); and in Saxeville in Waushara County ( Wisconsin).

In Germany, whitlockite found in the " Rotläufchen Mine" at Waldgirmes in Hesse; at the crest of the mountain at Joldelund in Schleswig-Holstein and in the now-closed Absetzerhalde of Lichtenberg open pit at Ronneburg. In Austria whitlockite could previously only be found on Millstaetter lake at Laggerhof.

Other localities lie in Algeria, in the Lesser Antilles island of Anguilla, Argentina, Australia, the Bahamas, China, Curacao, Israel, Canada, Cuba, Malaysia, Mexico, Namibia, Norway, Poland, Puerto Rico, Russia, Saint Helena, Saudi Arabia, Spain, South Africa and Venezuela.

Crystal structure

Whitlockite crystallized trigonal space group R3c ( Raumgruppen-Nr. 161) with the lattice parameters a = 10.33 Å and c = 37.10 Å and 6 formula units per unit cell.