Gyrolith
| Gyrolith | |
|---|---|
.JPG) |
|
| General and classification | |
| other names |
|
| chemical formula | NaCa 16 [(OH) 8 | (Si, Al) 24 O 60 ] • 14H 2 O |
|
Mineral class (and possibly department) |
Silicates and germanates - layered silicates |
|
System no. to Strunz and to Dana |
9.EE.30 ( 8th edition : VIII / H.34) 73.02.02c.01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Room group (no.) | P 1 (No. 2) |
| Lattice parameters |
a = 9.74 Å ; b = 9.74 Å; c = 22.40 Å α = 95.7 °; β = 91.3 °; γ = 120.0 ° |
| Formula units | Z = 1 |
| Physical Properties | |
| Mohs hardness | 3 to 4 |
| Density (g / cm 3 ) | measured: 2.388 to 2.390; calculated: 2.40 |
| Cleavage | completely after |
| Break ; Tenacity | not defined |
| colour | colorless to white, greenish, yellowish, brownish |
| Line color | White |
| transparency | transparent to opaque |
| shine | Glass gloss, pearlescent |
| Crystal optics | |
| Refractive indices |
n α = 1.535 n β = 1.548 n γ = 1.549 |
| Birefringence | δ = 0.014 |
| Optical character | uniaxial negative |
Gyrolith is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the triclinic crystal system with the composition NaCa 16 [(OH) 8 | (Si, Al) 24 O 60 ] · 14H 2 O, so it is chemically a water-containing sodium - calcium- silicate. Structurally, it belongs to the layered silicates .
Gyrolith mainly forms radial to spherical mineral aggregates , which consist of pseudo-hexagonal, fibrous to tabular crystals . In its pure form, the mineral is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear white and, due to foreign admixtures, take on a greenish, yellowish or brownish color, the transparency decreasing accordingly.
Etymology and history
Gyrolith was first discovered on the well-known rock needle "The Old Man of Storr " (short: The Storr or Storr , about 9 miles from Portree ) on the Scottish "Isle of Skye " and described in 1851 by Thomas Anderson, who described the mineral because of its characteristic Crystal form named after the Greek word γύρος for circle , top or rotation .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Gyrolith belonged to the department of " phyllosilicates (phyllosilicates)" where he collaborated with Armstrongit , fedorite , Lalondeit , Martinit , Minehillit , Orlymanit , Reyerit , Truscottite , Tungusit and Zeophyllite the "Reyerite group" with the system no. VIII / H.34 .
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 Gyrolith in the "layered silicates" department. This is, however, further subdivided according to the layer structure, so that the mineral, according to its structure, can be found in the sub-section "Simple tetrahedral networks of 6-membered rings, connected by octahedral networks or bands", where it is only together with tungusite, the unnamed group 9.EE.30 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Gyrolith to the class of "silicates and Germanates" and there in the department of "phyllosilicates with condensed tetrahedral layers". Here he is the only member of the " Reyerite group (Gyrolith sub-group) " with system no. 73.02.02c within the sub-section “Layered Silicates: Condensed Tetrahedron Layers with Double and Single Layers”.
Education and Locations
Gyrolith formed by material exchange in addition to rocks, geodes , amygdaloids and as crack filling in basalts , but can also hydrothermally converted rhyolites and sediments and some ore - deposits arise. The accompanying minerals include apophyllite , calcite , laumontite , okenite , stilbite , thomsonite , tobermorite and xonotlite .
As a rare mineral formation, Gyrolith could only be proven at a few sites, whereby so far (status: 2013) around 100 sites are known. In addition to its Storr type locality , the mineral was discovered in the United Kingdom in several locations on the Isle of Skye and the Isle of Mull in Scotland and in the historic County of Antrim in Northern Ireland.
In Germany, Gyrolith is known from the Zeilberg in Bavaria, from the quarries "Hochberg" and "Gaulsberg" in Vogelsberg in Hesse , from Bramburg near Adelebsen in Lower Saxony and from Arensberg and Ettringer Bellerberg (quarry "Caspar" near Ettringen ) in Rhineland- Palatinate.
Other sites are in Australia, China, Costa Rica, Denmark, France and French Polynesia, Greenland, India, Iceland, Israel, Italy, Japan, Canada, Norway, Portugal, Romania, Russia, Slovakia, the Czech Republic, the Ukraine and in the United States of America (USA).
Crystal structure
Gyrolith crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 9.74 Å ; b = 9.74 Å; c = 22.40 Å; α = 95.7 °; β = 91.3 ° and γ = 120.0 ° and one formula unit per unit cell .
See also
literature
- Thomas Anderson: Description and analysis of gurolite, a new mineral species , In: The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science , Volume 1 (1851), pp. 111–113 ( PDF 239.5 kB )
- M. Fleischer: New mineral names , In: American Mineralogist , Volume 44 (1959), pp. 464–470 ( PDF 444 kB ; p. 7: Centrallasite = Gyrolite)
Web links
Individual evidence
- ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 765 (first edition: 1891).
- ↑ 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. 682 .
- ↑ Gyrolite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 78.9 kB )
- ↑ a b Mindat - Gyrolite
- ↑ Mindat - Number of localities for Gyrolite
- ↑ Find location list for Gyrolith at the Mineralienatlas and at Mindat