Sapphirin

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Sapphirin
Sapphirine (Madagascar) .jpg
Sapphirin and phlogopite (reddish) from Madagascar
General and classification
chemical formula
  • (Al, Mg) 8 [O 2 | (Al, Si) 6 O 16 ]
  • (Mg 3.5 Al 3.5 ) Al [O 2 | Al 4.5 Si 1.5 O 18 ]
Mineral class
(and possibly department)
Silicates and Germanates
System no. to Strunz
and to Dana
9.DH.45 ( 8th edition : VIII / F.15)
69.02.01b.01
Similar minerals Aenigmatite
Crystallographic Data
Crystal system triclinic or monoclinic
Crystal class ; symbol triclinic pinacoidal; 1 or monoclinic prismatic; 2 / m
Space group P 1 (No. 2) or P 2 1 / a (No. 14, position 3)Template: room group / 2Template: room group / 14.3
Lattice parameters see crystal structure
Formula units see crystal structure
Frequent crystal faces (100), (101), (110), (010), (011)
Physical Properties
Mohs hardness 7.5
Density (g / cm 3 ) measured: 3.40 to 3.58; calculated: 3.486
Cleavage good after {010}, indistinct after {001} and {100}
Break ; Tenacity slightly mussel-like
colour light to dark blue or green, white, gray, light red, yellow
Line color White
transparency translucent to opaque
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.703 to 1.729
n β  = 1.703 to 1.732
n γ  = 1.705 to 1.734
Birefringence δ = 0.004 to 0.005
Optical character biaxial negative
Axis angle 2V = 51 to 69 ° (measured); 78 to 88 ° (calculated)
Pleochroism visible:
X = colorless, light reddish, yellowish green, light yellow
Y = sky blue, lavender blue, bluish green
Z = blue, sapphire blue, dark blue

Sapphirin , occasionally sapphirine written, is a rarely occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the simplified chemical composition (Al, Mg) 8 [O 2 | (Al, Si) 6 O 16 ]

Sapphirin is transparent to translucent and forms only weakly developed crystals with a tabular to leafy habit . It is mostly found in the form of granular masses. Its color generally varies between light to dark blue or green, but white, gray, light red and yellow color varieties are also known.

Etymology and history

The name sapphirin indicates that it is similar in color to sapphire . However, various other gemstones that could be mistaken for sapphire have been referred to as sapphirin in the past , such as blue chalcedony and blue spinel .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the sapphirin belonged to the department of " chain and band silicates (inosilicates)", where together with khmaralith and surinamite it formed the unnamed group VIII / F.15 .

The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also classifies sapphirin in the category of “chain and band silicates (inosilicates)”. This is, however, further subdivided according to the type of chain formation, so that the mineral, according to its structure, can be found in the sub-section “Chain and band silicates with 4-periodic single chains, Si 4 O 12 ”, where together with Rhönite it is group 9 .DH.45 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns sapphirin to the class of "silicates and germanates", but there in the department of "chain silicates: chains with side branches or loops". Here it is together with Surinamite and Khmaralith in the group "Aenigmatite and related species (sapphirin subgroup)" with the system no. 69.02.01b can be found in the subsection " Chain silicates: chains with side branches or loops with P> 2 ".

Crystal structure

Two structural modifications are known of sapphirin:

Sapphirin-1A crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a  = 9.97  Å ; b  = 10.34 Å; c  = 8.62 Å; α = 107.4 °; β = 95.2 ° and γ = 123.8 ° as well as 2 formula units per unit cell . Template: room group / 2

Sapphirin-2M crystallizes monoclinically in the P 2 1 / a (No. 14, position 3) with the lattice parameters a  = 11.27 Å; b  = 14.40 Å; c  = 9.93 Å and β = 125.5 ° and 4 formula units per unit cell . Template: room group / 14.3

Education and Locations

Sapphirin is a typical mineral in metamorphic rocks that are formed under high temperatures and at medium to high pressures ( granulite facies or eclogite facies ). At temperatures above 900 ° C, sapphirin can form in metamorphic pelites , and it is also found in mafic granulites and pegmatites .

See also

Web links

Commons : Sapphirin  - Collection of images, videos and audio files

Individual evidence

  1. a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
  2. a b c d 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.  644 .
  3. a b c Sapphirine , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 75.6 kB )
  4. a b c Mindat - Sapphirine
  5. G. Strübel, S. Zimmer: Lexicon of Minerals. Enke Verlag, Stuttgart, 1991; ISBN 3-432-92722-3
  6. Froitzheim, N., I. Miladinova, M. Janák, K. Kullerud, EK Ravna, J. Majka, ROC Fonseca, C. Münker and TJ Nagel (2016): Devonian subduction and syncollisional exhumation of continental crust in Lofoten, Norway . Geology 44 (3), pp. 223-226
  7. K. Bucher, M. Frey: Petrogenesis of Metamorphic Rocks. Springer Verlag, Berlin, 2002; ISBN 3-540-43130-6