Apatite

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Apatite
Apatite Canada.jpg
Québec / Canada
General and classification
chemical formula Ca 5 [(F, Cl, OH) | (PO 4 ) 3 ]
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.BN.05 ( 8th edition : VII / B.39)
41.08.01.00
Similar minerals Beryl , diopside , tourmaline group
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal dipyramidal, 6 / m
Frequent crystal faces {10 1 0}, {0001}, {10 1 1}
Physical Properties
Mohs hardness 5
Density (g / cm 3 ) 3.2
Cleavage imperfect
Break ; Tenacity shell-like, brittle
colour colorless, green, brown or white
Line color White
transparency transparent to opaque
shine Glass gloss, fat gloss
Crystal optics
Refractive indices n ω  = 1.631 to 1.675
n ε  = 1.627 to 1.668
Birefringence δ = 0.004 to 0.014
Optical character uniaxial negative
Pleochroism green apatite slightly yellow, blue apatite very strong blue and colorless
Other properties
Chemical behavior soluble in ENT 3
Special features after heating phosphorescence

Apatite ( the apatite) is the short and collective name for a group of chemically similar, but unspecified minerals with the following members:

Mineral name former name chemical composition
Fluoroapatite Apatite (CaF) Ca 5 [F | (PO 4 ) 3 ]
Chlorapatite Apatite (CaCl) Ca 5 [Cl | (PO 4 ) 3 ]
Hydroxyapatite Apatite (CaOH) Ca 5 [OH | (PO 4 ) 3 ]
Fluorostrophite Apatite (SrOH) and strontium apatite (Sr, Ca) 5 [(F, OH) | (PO 4 ) 3 ]
Carbonate fluoroapatite Carbonate fluorapatite Ca 5 [F | (PO 4 , CO 3 OH) 3 ]
Carbonate hydroxyapatite Carbonate hydroxyapatite Ca 5 [OH | (PO 4 , CO 3 OH) 3 ]
Hydroxyapatite-M Apatite- (CaOH) -M and clinohydroxyapatite (Ca, Na) 5 [(OH, Cl) | (PO 4 , SO 4 ) 3 ]

Apatite is also the namesake of the apatite- pyromorphite group with a high (up to 100%) and freely exchangeable concentration of simply negative fluorine , chlorine or hydroxide ions . The general chemical formula for apatite is Ca 5 [(F, Cl, OH) | (PO 4 ) 3 ].

All minerals belong to the mineral class of " phosphates , arsenates and vanadates " and crystallize in the hexagonal crystal system with the general chemical composition (Ca, Ba, Pb, Sr etc.) 5 [(F, Cl, OH) | (PO 4 , CO 3 OH) 3 ] and develop mostly tabular to prismatic crystals , but also kidney to grape-like, spherical, granular, fibrous and massive mineral aggregates as well as stalagmite forms and crusty coatings of variable, but often green, brown or white color.

With a Mohs hardness of 5, apatites are among the medium-hard minerals that can still be scratched with a knife. They serve as a reference mineral in the hardness scale of the same name. Depending on the composition, the apatites have a density of 3.1 to 3.8 g / cm 3 .

etymology

The name apatite is derived from the ancient Greek απατάω apatáo , German ' to deceive' , and was coined in 1786 by the German geologist Abraham Gottlob Werner . Since the mineral comes in so many shapes and colors, there is a high risk that it will be confused with other minerals such as beryl , topaz or various tourmalines .

Single minerals and varieties

  • Fluorapatite - very common, either colorless or white, yellow, pink, blue, purple, green, brown
  • Chlorapatite - rather rare occurrence in white or various shades of yellow
  • Hydroxyapatite - rather rare occurrence in the colors white, various shades of gray or yellow
  • Apatite cat's eye
  • Asparagus stone - yellowish green
  • Mangualdit - apatite containing manganese
  • Moroxite - bluish-green, purple, red

Education and Locations

Apatite occurs hydrothermally in pegmatites and metamorphic limestone , but also forms in igneous rock or from organic material in sedimentary rock . Apatites often arise through biomineralization , be it in rock formations, in the ground, as undesirable plaque, in bones, etc .; but here always in very specific micro-environmental conditions.

Locations include Brazil , the People's Republic of China , India , Clear Lake / Ontario in Canada , Madagascar , Morocco , Mercado and Durango in Mexico , Myanmar (Upper Burma), Dusso in Pakistan , Kola Peninsula in the Russian Federation , Fiesch in Switzerland , Sri Lanka , Maine in the USA .

synthesis

Hydroxyapatite is synthesized using the Tiselius process:

In the first step, the compound bruschit (calcium hydrogen phosphate dihydrate, CaHPO 4 · 2H 2 O) is produced from calcium chloride solution (CaCl 2 ) and disodium hydrogen phosphate solution (Na 2 HPO 4 ) . The bruschit, which is very poorly soluble in water, is then boiled in sodium hydroxide solution (NaOH) until it has converted into hydroxyapatite.

Biological importance and use

In living beings

Hydroxyapatite is an important basic building block in the development of bone tissue . The osteoblasts are able to produce the mineral from phosphate and calcium ions and to incorporate hydroxyapatite variably into the bone. For example, the bones of the body skeleton consist of around 50%, the dentin (dentin) of around 70% and the enamel of around 97% hydroxyapatite. In kidney stones Shares may be contained apatite.

As a raw material

As a gem

Apatite, green, 2.66ct, Africa

Apatites are also increasingly important in the jewelry industry, especially gemstones with a cat's eye effect . However, processing is difficult due to the great sensitivity to acid and heat. Color changes are possible even with low heating or strong light.

See also

literature

  • WE Tröger, U. Bambauer, F. Taborsky and HD Trochim (1981): Optical determination of rock-forming minerals, Part 1: Determination tables . Stuttgart (Schweizerbarth).
  • Edition Dörfler: Mineralien Enzyklopädie , Nebel Verlag, ISBN 3-89555-076-0
  • Walter Schumann: Precious stones and gemstones , BLV Verlags-GmbH Munich (1976/1989), ISBN 3-405-12488-3
  • Schmittner Karl-Erich and Giresse Pierre, 1999. Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France. Sedimentology 46/3: 463-476.

Web links

Commons : Apatite  - collection of images, videos and audio files
Wiktionary: Apatit  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c d Mindat - Apatite group
  2. ↑ 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 , p.  466, 467 .
  3. ↑ a b c Stefan Weiss: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
  4. ↑ Patrick D. Roycroft, Martine Cuypers: The Etymology of The Mineral Name 'Apatite': A Clarification . In: Irish Journal of Earth Sciences . tape 33 , 2015, p. 71-75 , doi : 10.3318 / ijes.2015.33.71 , JSTOR : 10.3318 / ijes.2015.33.71 .