Smithsonite

Smithsonite
Bluish, grape-like smithsonite from the "Kelley Mine", New Mexico - exhibited in the Harvard Museum of Natural History
General and classification
other names	noble calamine or noble calamine Coal gall Zinc spar
chemical formula	Zn [CO 3 ]
Mineral class (and possibly department)	Carbonates and nitrates (formerly carbonates, nitrates and borates)
System no. to Strunz and to Dana	5.AB.05 ( 8th edition : Vb / A.02) 01/14/01/06
Crystallographic Data
Crystal system	trigonal
Crystal class ; symbol	ditrigonal-scalenohedral; 3  2 / m
Space group	R 3 c (No. 167)
Lattice parameters	a  = 4.65  Å ; c  = 15.03 Å
Formula units	Z  = 6
Physical Properties
Mohs hardness	4 to 4.5 or 4.5 to 5
Density (g / cm 3 )	4.3 to 4.5 (in pure form 4.43)
Cleavage	completely according to {10 1 1}
Break ; Tenacity	shell-like to uneven; brittle
colour	colorless to white with greenish, yellowish and bluish tones, also light to dark gray and brown
Line color	White
transparency	transparent to translucent
shine	Glass gloss to pearlescent gloss
Crystal optics
Refractive indices	n ω  = 1.842 to 1.850 n ε  = 1.619 to 1.623
Birefringence	δ = 0.223 to 0.227
Optical character	uniaxial negative
Other properties
Chemical behavior	Easily soluble in warm HCl with the release of CO 2
Special features	light green to light blue fluorescence possible

Smithsonit , as calamine , (Noble) calamine or Edelgalmei referred to is a common mineral of the mineral class of "carbonates and nitrates" with the chemical composition of Zn [CO ₃ ] and chemical terms zinc carbonate .

Smithsonite crystallizes in the trigonal crystal system , but rarely develops well-formed crystals with a rhombohedral or scalenohedral habit , which can then be up to 12 cm in size and show a glass-like sheen on the surface. Mostly, however, it is found in the form of grape, stalactitic or granular to coarse aggregates with surfaces that shimmer like mother-of-pearl.

In its pure form, smithsonite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also be translucent white and, due to foreign admixtures, take on a greenish, yellowish or bluish as well as light to dark gray and brown color.

Etymology and history

As calamine (also calamine ) is a mixture of Smithsonit and Hemimorphit (calamine) or else additionally with Hydrozinkit designated. The English mineralogist James Smithson (1765–1829) was the first to distinguish these minerals, and the mineral smithsonite was given its current name in his honor.

classification

In the outdated 8th edition of the mineral classification according to Strunz , the smithsonite belonged to the common mineral class of "carbonates, nitrates and borates" and there to the section "anhydrous carbonates without foreign anions ", where together with calcite , gaspéit , magnesite , otavite , rhodochrosite , Siderite and spherocobaltite form the "calcite group" with system no. Vb / A.02 formed.

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. V / B.02-60 . In the "Lapis system" this also corresponds to the section "Anhydrous carbonates [CO ₃ ] ²⁻ without foreign anions", where smithsonite together with calcite, gaspéite, magnesite, otavite, rhodochrosite, siderite, spherocobaltite and vaterite form the "calcite group." "Forms (as of 2018).

The 9th edition of Strunz's mineral systematics , valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, assigns the smithsonite to the newly defined class of “carbonates and nitrates”, but also to the “carbonates without additional” class Anions; without H ₂ O “. This is, however, further subdivided according to the element groups whose representatives are contained in the minerals, so that the mineral can be found according to its composition in the subsection "alkaline earth (and other M ²⁺ ) carbonates", where it is also found together with calcite, Gaspéit, magnesite, otavite, rhodochrosite, siderite and spherocobaltite form the "calcite group" with system no. 5.AB.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the smithsonite, like the outdated Strunz'sche systematics, to the common class of "carbonates, nitrates and borates" and there to the department of "anhydrous carbonates". Here, too, it is in the "Calcite group (trigonal: R 3 c )" with the system no. 01/14/01 to be found in the subsection “ Anhydrous carbonates with simple formula A ⁺ CO ₃ ”.

Chemism

In a pure composition, smithsonite consists of 52.15% zinc (Zn), 9.58% carbon (C) and 38.28% oxygen (O). However, it can sometimes contain high levels of iron (Fe) and manganese (Mn), which are known as ferro-smithsonite (synonym monheimite ) or manganese-smithsonite . Smithsonite can also contain small amounts of calcium , lead , copper , magnesium and cadmium , and traces of germanium and indium . Often, smithsonite is also contaminated with iron oxide and aluminum silicate .

The cadmium content of some Smithsonites can be traced back to mixed crystal formation with Otavit (Cd [CO ₃ ]).

Crystal structure

Smithsonite crystallizes trigonal in the space group R 3 c (space group no. 167) with the lattice parameters a  = 4.65  Å and c  = 15.03 Å and six formula units per unit cell .

Smithsonite is isotypic with calcite .

properties

Purple smithsonite from the USA

Pure smithsonite is colorless. However, by incorporating additional ions into the crystal system, it can take on different colors. The bluish color is caused by the addition of copper ions and the pale pink to violet color by cobalt ions .

With a Mohs hardness of 4 to 5, smithsonite is one of the medium-hard minerals that can be scratched with a pocket knife , similar to the reference minerals fluorite (hardness 4) and apatite (hardness 5). Its density is between 4.3 and 4.5 (in pure form 4.43) g / cm³ and is comparable to the light metal titanium .

When heated strongly, smithsonite breaks down into zinc oxide . This decay was previously used, among other things, for qualitative evidence: sublimed zinc oxide is deposited on carbon in front of the soldering tube. This is lemon yellow when hot (see also zinc suboxides ) and only takes on the typical white color of zinc oxide when it has cooled down.

Smithsonite shows green, blue-white, pink, or brown fluorescence on various occasions .

Modifications and varieties

Particularly iron and manganese rich varieties which means between species calamine one hand, and siderite or rhodochrosite form the other hand, are as Zinkeisenspat , Eisenzinkspat and Manganzinkspat been designated.

Education and Locations

Rare crystalline formation of smithsonite in colorless, transparent crystals from the Tsumeb Mine, Otjikoto region, Namibia (size 3.9 cm × 2.8 cm × 2.3 cm)

Smithsonite is formed by oxidation in different descending, primary zinc ore veins. It is found there mostly in small crystals , more often in kidney-shaped, shell-like aggregates, in stalactitic, also coarse in dense and earthy masses and forms nests , stocks and beds , especially in calcareous and dolomitic rocks of various formations in the Eschweiler-Stolberg area in the Rhineland , near Wiesloch in Baden, as a coating on calcite crystals in Rammelsberg near Goslar / Harz , near Tarnowitz in Silesia, also in Carinthia , Styria , Belgium (here led to the political curiosity Neutral Moresnet ), England , on the island of Thasos in Greece . Smaller deposits were mined in the Gurgltal in the Tyrolean Oberland in the 15th century (see also Knappenwelt Gurgltal ) and in Germany in the 19th century in the area of Iserlohn , Brilon (already in the 17th century) and Inzell (Bavaria).

Other locations include Broken Hill in Australia , Tsumeb in Namibia , Magdalena / New Mexico in the USA . So far (as of 2009) around 1600 sites are known worldwide.

use

As a raw material

Smithsonite, along with other calamine minerals, was used as a zinc supplier for the manufacture of brass until the end of the 18th century . This previously common process was cementation , in which the calamine was added directly to the lump copper as an aggregate. The zinc , which dissociates in gaseous form from the calamine when heated, diffuses into the copper platelets; brass is formed as an alloy . This has been called the "Dutch way" of making brass. For a long time, however, it was not recognized that calamine was the source of the zinc required for the brass, but rather was thought to be a kind of dye that colored the red copper golden yellow.

As a gem

Blue, banded and cloudy smithsonite, various cabochons

Smithsonite is one of the little-known gemstones due to its relative softness . Nevertheless, it is in great demand because of its appealing blue-green to violet color and its occasionally iridescent pearlescent sheen and is processed accordingly into pieces of jewelery or as a tumbled stone into so-called "hand flatterers". Since Smithsonite is mainly found in translucent aggregates, the cabochon cut is preferred .

Smithsonite is similar in appearance to the minerals and gemstones turquoise , the quartz variety chrysoprase , the pectolite variety larimar and jade , but also correspondingly colored calcites , hemimorphites and aragonites and is partly imitated by them . Proof of authenticity should therefore be requested when purchasing expensive pieces.

Ecological importance

The calamine particle grows on calamine-rich soils, is very rare today and, in contrast to conventional violets, is yellow. Quite a number of Galmeivilchenflurs are under nature protection in the Aachen city region .

See also

• Systematics of the minerals
• List of minerals
• Calamine (mixture of substances)

literature

• Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 571 (first edition: 1891).
• Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 64, 283 .
• Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 113 .
• Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 214 .

Web links

Commons : Smithsonit  - collection of pictures, videos and audio files

• Mineral Atlas: Smithsonite (Wiki)
• Smithsonite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on October 15, 2019 . 
• American-Mineralogist-Crystal-Structure-Database - Smithsonite. In: rruff.geo.arizona.edu. Retrieved October 15, 2019 . 
• Calamine. In: zinkhuetterhof.de. Zinkhütter Hof, archived from the original on April 15, 2017 ; accessed on October 15, 2019 . 
• Smithsonite. In: realgems.org. March 26, 2012, accessed on October 15, 2019 (with image examples of cut stones). 

Individual evidence

1. ↑ Zinkspat, Smithsonit, Galmei, Kohlengalmei , in: F. Klockmann: Textbook Der Mineralogie , Aachen 1903 in the Google book search
2. ↑ ^{a b c d} 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.  286 (English).
3. ^ David Barthelmy: Smithsonite Mineral Data. In: webmineral.com. Retrieved October 15, 2019 .  
4. ↑ ^{a b c} Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
5. ↑ ^{a b c d e} 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.  712 .
6. ^ ^{A b} Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  526 .
7. ↑ ^{a b c d e f g} Smithsonite . 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; 66  kB ; accessed on October 15, 2019]).
8. ↑ ^{a b c} Smithsonite. In: mindat.org. Hudson Institute of Mineralogy, accessed October 15, 2019 .  
9. ^ Meyers Konversations-Lexikon, 1888. Can be viewed online here
10. ↑ Martin Okrusch, Siegfried Matthes: Mineralogie. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 64 .
11. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed October 15, 2019 .  
12. ↑ Mineral Atlas: Monheimite
13. ↑ Find location list for Smithsonite at the Mineralienatlas and at Mindat
14. ↑ Calamine. In: zinkhuetterhof.de. Zinkhütter Hof, archived from the original on April 15, 2017 ; accessed on October 15, 2019 .  
15. ^ Smithsonite imitations. In: epigem.de. Gemstone Testing Institute (EPI), accessed October 15, 2019 .