Nakrit
| Nakrit | |
|---|---|
 |
|
| General and classification | |
| other names |
Stone marrow |
| chemical formula | Al 4 [(OH) 8 | Si 4 O 10 ] |
|
Mineral class (and possibly department) |
Silicates (and germanates) - layered silicates (phyllosilicates) |
|
System no. to Strunz and to Dana |
9.ED.05 ( 8th edition : VIII / H.25) 01/01/01/03 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic; m |
| Space group | Cc (No. 9) |
| Lattice parameters |
a = 8.91 Å ; b = 5.15 Å; c = 15.70 Å β = 113.7 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2 to 2.5 |
| Density (g / cm 3 ) | measured: 2.5 to 2.7; calculated: 2.582 |
| Cleavage | completely after {001} |
| Break ; Tenacity | uneven |
| colour | colorless, white, gray, yellow-brown |
| Line color | White |
| transparency | transparent to translucent |
| shine | earthy, pearlescent finish |
| Crystal optics | |
| Refractive indices |
n α = 1.557 n β = 1.562 n γ = 1.563 |
| Birefringence | δ = 0.006 |
| Optical character | biaxial negative |
| Axis angle | 2V = 40 ° (measured); 48 ° (calculated) |
| Other properties | |
| Chemical behavior | soluble in H 2 SO 4 when heated |
Nakrit , also known as stone marrow , is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the chemical composition Al 4 [(OH) 8 | Si 4 O 10 ], and is therefore seen crystal chemically an aluminum - phyllosilicate with hydroxide ions ((OH) 2 ) as an additional anions .
Nakrit usually develops earthy, scaly or massive aggregates , rarely also small, tabular, irregular pseudo-hexagonal crystals of white, gray or yellowish-brown color and pearlescent sheen.
Etymology and history
Nakrit was first discovered in the unity mine, more precisely "unity treasure trove" near Brand-Erbisdorf in the German district of Central Saxony and described in 1807 by Alexandre Brongniart , who named the mineral after the French word nacre for mother-of-pearl because of its sheen .
In the mining landscape of Brand-Erbisdorf, silver has been mined since at least the 17th century and in 1850 the Hörnigschacht (first mentioned in 1518) was merged with other mines to form the “Unity Fundgrube”. Of the now closed pit, only the hut house , which has been converted into a museum, remains . In addition to silver and nacrite, another 25 minerals were discovered in the type locality , such as the lead minerals galena and pyromorphite , the antimony silver cover pyrargyrite , the antimony luster stibnite , the zinc cover sphalerite and the jewelry minerals opal , quartz , rhodochrosite and schörl . In addition, it was found as quartz varieties nor the Chalcedon and its sub-variety Jasper .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of nacrite belonged to the general ward of " phyllosilicates (phyllosilicates)" where he collaborated with dickite , halloysite 7 Å and kaolinite the "kaolinite-group" with the system No. VIII / H.25 .
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 nakrit in the category of "phyllosilicates". This is, however, further subdivided according to the structure of the layers, so that the mineral can be found in the sub-section "Layered silicates (phyllosilicates) with kaolinite layers, composed of tetrahedral or octahedral networks", where it can be found together with dickite, kaolinite and odinite the "kaolinite group" with the system no. 9.ED.05 forms.
The systematics of minerals according to Dana , which is predominantly used in the English-speaking world , also classifies nakrit in the “layered silicate minerals” section. Here it is together with dickite, kaolinite, halloysite-7Å, endellite and odinite in the "kaolinite group" with the system no. 71.01.01 can be found in the sub-section “ Layered Silicates: Layers of six-membered rings with 1: 1 layers ”.
Crystal structure
Nakrit crystallizes in the monoclinic crystal system in the space group Cc (space group no. 9) with the lattice parameters a = 8.91 Å , b = 5.15 Å, c = 15.70 Å and β = 113.7 ° and 2 formula units per Unit cell .
Modifications and varieties
A coarse-scaled variety of nakrite is known as pholerite .
Education and Locations
Nakrite forms in the cavities of hydrothermal deposits . Accompanying minerals include calcite , dolomite , fluorite , quartz and topaz .
As a rare mineral formation, nakrit has so far (as of 2012) only been proven at a few sites, with around 100 sites being known. In addition to its type locality Grube Einigkeit near Brand-Erbisdorf , the mineral appeared in Germany in several other mines in the Saxon Ore Mountains . Other locations include Schweighausen in the Black Forest in Baden-Württemberg; Bad Berneck, Joditz and Wölsendorf (Schwandorf) in Bavaria, Sankt Andreasberg in Lower Saxony's Harz Mountains, the Zollverein , Julia and Wilder Mann collieries in North Rhine-Westphalia, Bad Ems and Dannenfels in Rhineland-Palatinate, the Korb mine near Eisen (Nohfelden) in Saarland as well as Ronneburg and in the Henneberg quarry near Weitisberga in Thuringia.
In Austria, nakrit has so far only been found on Katschberg , more precisely in rock samples that were taken during the construction of the Katschberg tunnel for the Tauern Autobahn between Carinthia and Salzburg .
Other locations include Argentina, Australia, Bolivia, China, France, Italy, Japan, Canada, Kazakhstan, the Democratic Republic of the Congo, Mexico, Namibia, Poland, Sweden, Slovakia, Spain, South Africa, South Korea, the Czech Republic, Ukraine, Hungary, Great Britain (UK) and the United States of America (USA).
See also
literature
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 258 .
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 760 (first edition: 1891).
Web links
- Mineral Atlas: Nakrit (Wiki)
- Nacrite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on May 3, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Nacrite. In: rruff.geo.arizona.edu. Retrieved May 3, 2019 .
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 675 (English).
- ↑ David Barthelmy: Nacrite Mineral Data. In: webmineral.com. Retrieved May 3, 2019 .
- ↑ a b Nacrite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 70 kB ; accessed on May 3, 2019]).
- ↑ a b c d Nacrite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 3, 2019 .
- ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 841 .
- ↑ mining landscape Freiberg Mining Landscape Brand-Erbisdorf. In: montanregion-erzgebirge.de. Welterbe Montanregion Erzgebirge eV, accessed on May 3, 2019 .
- ↑ Stefan Schorn and others: Type locality Grube Unity. In: mineralienatlas.de. Mineral Atlas , accessed May 3, 2019 .
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 565 .
- ↑ Localities for nacrites. In: mindat.org. Hudson Institute of Mineralogy, accessed May 3, 2019 .