Sapphirine

• (Al, Mg) 8 [ O2 | (Al, Si) 6O16 ]
• ( Mg3.5Al3.5 ) Al [ O2 | Al4.5Si1.5O18 ]

X = colorless, light reddish, yellowish green, light yellow Y = sky blue, lavender blue, bluish green Z = blue, sapphire blue, dark blue

Sapphirine, sapphirine also occasionally 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 [ O2 | (Al, Si) 6O16 ]

Sapphirine is transparent to translucent and is only weakly developed crystals with tabular to leafy habit of. He usually can be found in the form of granular masses. Its color varies generally from light to dark blue or green, but also white, gray, bright red and yellow color varieties are known.

Etymology and history

The name refers to the sapphirine the sapphire -like color. However, in the past, various other gemstones that can be confused with sapphire, known as sapphirine, such as blue chalcedony and blue spinel.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the sapphirine belonged to the department of " chains and chain silicates ( inosilicates ) ", where he led the unnamed group VIII/F.15 formed together with Khmaralith and Surinamit.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the sapphirine also included in the department's " chain and chain silicates ( inosilicates ) ". However, this is further subdivided according to the type of chain formation, so that the mineral is "with 4 -periodic single chains, chain and chain silicates Si4O12 " to find according to its construction in the subdivision where it 9.DH. together with Rhönit the unnamed group 45 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the sapphirine in the class of " silicates and Germanates " there, however, in the department of " chain silicates: chains with side branches or loops " one. Here he is with Surinamit and Khmaralith in the group " Aenigmatit and related species ( sapphirine subgroup ) " with the system no. 69.02.01b within the subdivision " chain silicates: > 2 chains with side branches or loops with P" to find.

Education and Locations

Sapphirine is a typical mineral in metamorphic rocks that have arisen under high temperatures and at moderate to high pressures ( granulite ). At temperatures above 900 ° C in metamorphic pelites form sapphirine, as it is found in mafic granulites and in pegmatites.

Crystal structure

From sapphirine two structural modifications are known:

Sapphirine -1A crystallizes in the triclinic space group P1 ( Raumgruppen-Nr. 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 ° and two formula units per unit cell.

Sapphirine -2M crystallizes in the monoclinic space group P21 / a ( Raumgruppen-Nr. 14) with the lattice parameters a = 11.27 Å; b = 14.40 Å; c = 9.93 Å and 125.5 ° and β = 4 formula units per unit cell.