Whitlockite
| Whitlockite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ca 9 (Mg, Fe) [PO 3 OH | (PO 4 ) 6 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.AC.45 ( 8th edition : VII / A.05) 03/38/04/01 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-pyramidal 3 m |
| Room group (no.) | R 3 c (No. 161) |
| Lattice parameters | a = 10.33 Å ; c = 37.10 Å |
| Formula units | Z = 6 |
| Frequent crystal faces | rhombohedral {01 1 2}, tabular {0001} with {11 2 0} or {10 1 4} |
| Physical Properties | |
| Mohs hardness | 5 |
| Density (g / cm 3 ) | measured: 3.12; calculated: 3.102 |
| Cleavage | no |
| Break ; Tenacity | uneven to slightly scalloped |
| colour | colorless, white, gray, yellowish |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, weak resin gloss, matt |
| Crystal optics | |
| Refractive indices |
n ω = 1.629 n ε = 1.626 |
| Birefringence | δ = 0.003 |
| Optical character | uniaxial negative |
| Other properties | |
| Special features | piezoelectric and pyroelectric |
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 Ca 9 (Mg, Fe) [PO 3 OH | (PO 4 ) 6 ] and develops mostly tabular or rhombohedral crystals , but also granular mineral aggregates and microcrystalline crusts. The formation of cave pearls is also possible. Visible crystal surfaces have a glass-like or resin-like gloss , while crusty formations are rather matt.
Pure whitlockite is colorless and transparent. However, it can appear white due to multiple refraction due to multicrystalline formation or lattice construction defects and, due to foreign admixtures, it can take on a gray or yellowish color, the transparency decreasing accordingly. However, the line color is always white.
With a Mohs hardness of 5, whitlockite is one of the medium-hard minerals that, like the reference mineral apatite, can still be scratched with a knife.
Special properties
The mineral is piezoelectric and pyroelectric , so changes its electrical polarization with periodic pressure or temperature changes and thus builds up an electrical voltage.
Etymology and history
Whitlockite was first discovered by Harold J. Verrow in the “Palermo No. 1 Mine ”near 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 for minerals and precious stones at the American Museum of Natural history .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the whitlockite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates without foreign anions ", where it belongs together with brianite , farringtonite , panethite , Stanfieldit , Strontiowhitlockit and Tuit formed a separate group.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns whitlockite to the class of "phosphates, arsenates and vanadates" and there to the category of "phosphates etc. without additional anions ; without H 2 O “. However, this section is further subdivided according to the size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With medium-sized and large cations”, where the “whitlockite group” with the system no. 8.AC.45 and the other members bobdownsite , ferromerrillite , merrillite , strontiowhitlockite and tuit.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns whitlockite to the class of "phosphates, arsenates and vanadates" and there in the department of "anhydrous phosphates etc.". Here he is also the namesake of the "Whitlockit group" with the system no. 03/38/04 and the other members bobdownsite, ferromerrillite, merrillite, merrillite (Ca) , merrillite (Y) , strontiowhitlockite and tuit within the subdivision of " anhydrous phosphates etc., (A + B 2+ ) 3 (XO 4 ) 2 ”.
Education and Locations
Whitlockite is formed as a rare secondary mineral by hydrothermal processes of primary phosphates in granitic - Pegmatiten rare but also in sediments such as phosphorite . Whitlockite can also be found in the form of cave pearls . In stone meteorites, especially in chondrites , whitlockite (besides apatite ) occurs regularly. Whilockite was also found in the silicate inclusions of the IAB iron meteorite country. Furthermore, whitlockite can emerge from the action of liquid excrement from seabirds (e.g. penguins or cormorants) on limestone. It is part of the guano that forms in this way .
Depending on the formation conditions, whitlockite can occur in association with various minerals , including ludlamite , fairfieldite , triphyline , siderite , apatite and quartz in pegmatites; with hydroxyapatite in cavities and stanfieldite , farringtonite and brianite in meteorites.
In total, whitlockite has so far (as of 2011) been found at 65 sites. In addition to its type locality “Palermo No. 1 Mine “at Groton, the mineral occurred in the USA at Hyampom in Trinity County (California) ; in the Woodbine Meteorite in Jo Daviess County, Illinois; at Poland , Newry and Rumford (Maine) in Maine ; in the "Goldstrike Mine" near Lynn ( Eureka County ) and the "Twin Creeks Mine" near Potosi ( Humboldt County ) in Nevada; on Parker Mountain in Strafford County, New Hampshire; in the area of Custer, South Dakota; in the Crawford Mountains in Rich County, Utah; and at Saxeville in Waushara County, Wisconsin.
In Germany, whitlockite was found in the "Rotlaufchen Mine" near Waldgirmes in Hesse; on the Kammberg near Joldelund in Schleswig-Holstein and in the now closed waste dump of the Lichtenberg opencast mine near Ronneburg . In Austria, whitlockite has so far only been found on Lake Millstatt near Laggerhof.
Other locations are in Algeria , the small Antilles island of Anguilla , Argentina , Australia , the Bahamas , China , Curaçao , Israel , Canada , Cuba , Malaysia , Mexico , Namibia , Norway , Poland , Puerto Rico , Russia , Saint Helena , Saudi Arabia , Spain , South Africa and Venezuela .
Crystal structure
Whitlockite crystallizes trigonally in the space group R 3 c (space group no. 161) with the lattice parameters a = 10.33 Å and c = 37.10 Å as well as 6 formula units per unit cell .
See also
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X .
- ↑ Webmineral - Whitlockite (English)
- ↑ a b c d Handbook of Mineralogy - Whitlockite (English, PDF 64 kB)
- ↑ a b c Whitlockite at mindat.org (engl.)
- ↑ F.Heide, F. Wlotzka: Small meteorites, Springer-Verlag 1988th
- ↑ G, K, Benedix et al., Meteoritics and Planetary Science 35 (2000) 1127.
- ^ Mindat - Number of localities for whitlockite
literature
- Clifford Frondel: Whitlockite: A new calcium phosphate, Ca 3 (PO 4 ) 2 , in: American Mineralogist , Volume 26, pp. 145–152 ( PDF 472.4 kB )
Web links
- Mineral Atlas: Whitlockite (Wiki)