Serendibit
| Serendibit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ca 4 (Mg 6 Al 6 ) O 4 [Si 6 B 3 Al 3 O 36 ] |
|
Mineral class (and possibly department) |
Silicates and Germanates - chain silicates (inosilicates) |
|
System no. to Strunz and to Dana |
9.DH.45 ( 8th edition : VIII / F.14) 69.02.01a.06 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 10.010 (3) to 10.094 (3) Å ; b = 10.393 (3) to 10.478 (3) Å; c = 8.631 (2) to 8.694 (2) Å α = 106.36 (1) to 106.37 (1) °; β = 96.00 (l) to 96.10 (l) °; γ = 124.38 (1) to 124.40 (l) ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 6.5 to 7 |
| Density (g / cm 3 ) | measured: 3.42 to 3.52; calculated: 3.47 |
| Cleavage | good after {010} and {001} |
| colour | gray-blue, blue-green to deep blue, green, pale yellow, brown, black |
| Line color | White |
| transparency | transparent to opaque |
| shine | Glass gloss |
| radioactivity | no |
| Crystal optics | |
| Refractive indices |
n α = 1.701 n β = 1.703 n γ = 1.706 |
| Birefringence | δ = 0.005 |
| Optical character | biaxial positive |
| Axis angle | 2V = 80 ° |
| Pleochroism | strong: X = light yellow, yellow-green to blue-green; Y = almost colorless, light yellow, blue to blue-green; Z = light to dark blue |
Serendibite is a rare mineral from the mineral class of "silicates and germanates". It crystallizes in the triclinic crystal system with the idealized chemical composition Ca 4 (Mg 6 Al 6 ) O 4 [Si 6 B 3 Al 3 O 36 ] and structurally belongs to the chain silicates (inosilicates).
Natural serendibite always contains Fe 2+ and Fe 3+ and, depending on the iron content, is sky blue to intense dark blue with pronounced pleochroism (pale yellow green - dark blue). Serendibit rarely develops small, tabular crystals up to about two centimeters in size with a glass-like sheen on the surfaces. It is mostly found in the form of irregular grains. The crystals usually show polysynthetic twinning , which is often recognizable by the correspondingly striped crystal faces.
Etymology and history
Serendibite was first discovered in 1902 near the town of Gangapitiya in the central province of the island state of Sri Lanka . It was first scientifically researched and described by George T. Prior and Ananda K. Coomaraswamy the following year . The mineral got its name from the old Arabic name for "Sri Lanka" ( Serendib ).
classification
In the outdated but still partially in use 8th edition of the mineral classification by Strunz of Serendibite belonged to the department of " chain and chain silicates (inosilicates)" where he collaborated with aenigmatite , Dorrit , Høgtuvait , Krinovit , Makarochkinit , Rhönit , Sapphirin , Welshit and Wilkinsonite the "aenigmatite group" with the system no. VIII / F.14 .
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 classifies Serendibit 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 it can be found together with aenigmatite, baycovite , dorrite , Høgtuvait, Khmaralith , Krinovit, Makarochkinit , Rhönit , Sapphirin, Welshit and Wilkinsonit form the unnamed group 9.DH.45 .
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 aenigmatite, dorrit, Høgtuvait, krinovite, Makarochkinit, Rhönit, Welshit and Wilkinsonit in the group "Aenigmatite and related species (aenigmatite subgroup)" with the system no. 69.02.01a can be found in the subsection " Chain silicates: chains with side branches or loops with P> 2 ".
The current systematics of the CNMN for the sapphirin group rearranges them and groups the serendibit together with Høgtuvait, Makarochkinit, Rhönit and Welshit in the Rhönite group (Ca in the largest M position) below the sapphirin group in the sapphirin supergroup.
Crystal structure
Serendibite crystallizes in triclinic space group P 1 (space group no. 2) . The lattice parameters determined from three mineral samples are a = 10.010 (3) to 10.094 (3) Å ; b = 10.393 (3) to 10.478 (3) Å; c = 8.631 (2) to 8.694 (2) Å; α = 106.36 (1) to 106.37 (1) °; β = 96.00 (l) to 96.10 (l) ° and γ = 124.38 (1) to 124.40 (l) ° as well as two formula units per unit cell .
Education and Locations
Serendibite forms metasomatically at high temperatures when boron- containing solutions react with limestone and is found in skarns at the contact of limestone and granite , tonalite or granulite . It occurs there together with Fassaite , uvite-rich tourmaline , clinozoisite , spinel and calcite or diopside , spinel, scapolite , plagioclase , apatite . The formation of serendibit presumably presupposes SiO 2 - undersaturated conditions.
As a rare mineral formation, Serendibite could only be detected at a few sites, with around 20 sites being known to date (as of 2015). In addition to its type locality Gangapitiya in the central province, the mineral was only found in Sri Lanka in the Katukubura Hills near Kolonna in the province of Sabaragamuwa .
Other previously known sites are in the Mogok Valley in the Pyin U Lwin district (Pyin-Oo-Lwin, Mandalay Division) in Myanmar (Burma), in the Portage-du-Fort area in the Canadian province of Québec , on Mount Vohimena Ihosy (province of Fianarantsoa) as well as in Behara and Ianapera ( province of Toliara ) in Madagascar , in the iron-boron skarnen in the Aldan highlands of Eastern Siberia (Russia), in the district of Handeni in the region of Tanga in Tanzania as well as in several places in the US states California and New York .
Use as a gem stone
The majority of Serendibite is black and opaque, with transmitted light some show golden brown, green or blue shimmer. Serendibit is used almost exclusively as a collector's stone and gemstone. In 2005, new springs were found in Mogok , Myanmar , previously only three faceted stones from Sri Lanka were known.
While the Serendibit from Sri Lanka shows green-blue and violet-blue colors, the varieties from Myanmar are mostly black and opaque.
literature
- George T. Prior, Ananda K. Coomaraswamy: Serendibite, a new borosilicate from Ceylon. In: Mineralogical Magazine Volume 13 (1902), pp. 224–227 ( PDF 206.9 kB )
- Karl Schmetzer, George Bosshart, Heinz-Jurgen Burnhardt, Edward J. Gubelin and Christopher P. Smith: Serendibite from Sri Lanka. In: Gems & Gemology , Volume 38, 2002, pp. 73-79
Web links
- Mineral Atlas: Serendibit (Wiki)
- realgems.org - Serendibit (with image examples of cut Serendibite)
- Webmineral - Serendibite
- Database-of-Raman-spectroscopy - Serendibite
- American-Mineralogist-Crystal-Structure-Database - Serendibite
- IMA / CNMNC List of Mineral Names; March 2015 (PDF 1.5 MB; p. 159)
Individual evidence
- ↑ a b c ES Grew, UH Alenius, M. Pasero and J. Barbier: Recommended nomenclature for the sapphirine and surinamite groups (sapphirine supergroup) In: Mineralogical Magazine; August 2008 Volume 72 (4), pp. 839–876 ( PDF 2.82 MB )
- ↑ a b DG Van Derveer, GH Swihart, PK Sen Gupta, ES Grew: Cation occupancies in serendibite: a crystal structure study. In: American Mineralogist Volume 78 (1993), pp. 195–203 ( PDF 1.04 MB )
- ↑ a b c d e Serendibite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 76.2 kB )
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
- ↑ a b c d e Mindat - Serendibite
- ↑ a b GT Prior, AK Coomáraswámy: Serendibite, a new borosilicate from Ceylon In: Mineralogical Magazine Volume 13 (1903), pp. 224–227 ( PDF 207 kB )
- ↑ a b Ian Hutcheon, Avril E. Gunter, AN LeCheminant: Serendibite from Penrhyn Group marble, Melville Peninsula, District of Franklin In: The Canadian Mineralogist Volume 15 (1977), pp 108-112 ( PDF 1.68 MB )
- ↑ Mindat - Number of locations for Serendibit
- ↑ Find location list for Serendibit in the Mineralienatlas and Mindat