Otavit

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Otavit
Otavite-89481.jpg
White to almost colorless otavite crystals from the Tsumeb Mine, Namibia
General and classification
other names

Cadmium spar

chemical formula Cd [CO 3 ]
Mineral class
(and possibly department)
Carbonates (and relatives)
System no. to Strunz
and to Dana
5.AB.05 ( 8th edition : V / B.02)
01/14/01/07
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-scalenohedral; 3  2 / m
Space group R 3 c (No. 167)Template: room group / 167
Lattice parameters a  = 4.93  Å ; c  = 16.27 Å
Formula units Z  = 6
Frequent crystal faces {10 1 1}
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 4.96 (synthetic); calculated: 5.03
Cleavage completely according to {10 1 1}
colour colorless to white, yellowish brown to reddish brown
Line color White
transparency transparent to translucent
shine Glass luster to diamond luster; Pearlescent
Crystal optics
Refractive indices n ω  = 1.830
n ε  = 1.605
Optical character uniaxial negative
Other properties
Chemical behavior very easily soluble in hydrochloric acid
Special features red fluorescent

Otavit or cadmium spar is a rarely occurring mineral from the mineral class of "carbonates and nitrates" with the chemical composition Cd [CO 3 ] and is therefore a cadmium carbonate from a chemical point of view .

Otavit crystallizes in the trigonal crystal system and is mainly found in the form of crusty coatings, but rarely develops rhombohedral crystals up to about two millimeters in size.

Pure Otavit crystals are colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, Otavit can also appear white and take on a yellowish-brown to reddish-brown hue due to foreign admixtures. Visible crystal surfaces have a strong glass-like to diamond-like sheen , whereas microcrystalline, crusty shapes shimmer more like mother-of-pearl .

Etymology and history

Otavit was first discovered in the Tsumeb mine in Namibia and described in 1906 by Otto Schneider , who named the mineral after his area of ​​discovery, the Otavibergen .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , the Otavit belonged to the common mineral class of "carbonates, nitrates and borates " and there to the department of "anhydrous carbonates without foreign anions ", where together with calcite , gaspéit , Magnesite , rhodochrosite , siderite , smithsonite , spherocobaltite and vaterite formed the "calcite group".

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the Otavit to the class of “carbonates and nitrates” (the borates form a separate class here) and there to the “ Carbonates without additional anions; without H 2 O “. However, this section is further subdivided according to the type of cations involved , so that the mineral can be found according to its composition in the sub-section "alkaline earth (and other M 2+ ) carbonates", where it is found together with calcite, gaspéite, magnesite, rhodochrosite , Siderite, smithsonite and spherocobaltite the "calcite group" with the system no. 5.AB.05 forms.

The systematics of minerals according to Dana , like the outdated 8th edition of Strunz's systematics , assigns the Otavit to the common class of "carbonates, nitrates and borates" and there in the department of "anhydrous carbonates". Here it is together with calcite, magnesite, siderite, rhodochrosite, spherocobaltite, smithsonite and gaspéite in the "calcite group (trigonal: R-3c)" with the system no. 01/14/01 to be found in the subsection of " Anhydrous carbonates with simple formula A + CO 3 ".

Crystal structure

Otavit crystallizes trigonally in the space group R 3 c (space group no. 167) with the lattice parameters a  = 4.93  Å and c  = 16.27 Å and 6 formula units per unit cell . Template: room group / 167

properties

Like calcite, Otavit dissolves very easily in hydrochloric acid and foams up with a roaring noise. Hydrogen sulphide produces a yellow deposit of cadmium and a characteristic deposit of cadmium can also be seen on carbon in front of the soldering tube .

Under UV light , some Otavites show a red fluorescence , similar to that of neon-colored highlighters .

Education and Locations

Otavite (white, center of the picture) with malachite (green banded) and cerussite (colorless to white on malachite) from the Tsumeb Mine, Namibia Total size : 3.4 cm × 3 cm × 2.2 cm

Otavit forms as a rare secondary mineral in the oxidation zone of hydrothermal ore deposits . Accompanying minerals include azurite , calcite , cerussite , fluorite , hemimorphite , hydrozincite , malachite , oliveite , pyromorphite , rosasite and smithsonite .

As a rare mineral formation, Otavit could only be detected in a few places, whereby so far (as of 2018) around 20 sites have been documented worldwide. Its type locality Tsumeb Mine is the only known site in Namibia to date.

Water-filled Prangenhaus pit in Germany

In Germany, the Prangenhaus quarry near Wülfrath -Rohdenhaus, which belongs to the Flandersbach lime works and is now filled with water, is also known to have been found so far.

Within Europe, the mineral was found in the Esperanza mine near Lavrio in the Greek region of Attica, in the Sheshodonnell East mine near Carron in the west of Ireland, in the private lead ore deposit Su Elzu near Ozieri and the Miniera Montevecchio near Arbus on the Italian island Sardinia, in the Sasa mine near Probistip in the east of Macedonia, on Mount Boranja in the Podrinje district in Serbia , in a polymetallic deposit near Horní Rokytnice ( Oberrochlitz ) in Rokytnice nad Jizerou in the Czech Republic, near Zsidótemető in the Legyesbénye municipality in the north of Hungary as well as in the Coldstones quarry near Greenhow in the English county of North Yorkshire , in the Borrow pit near Bishopton in Scotland and in the Dolyhir quarry near Wethel in Wales in the United Kingdom (Great Britain).

Otavit is still known worldwide from the block 14 opencast mine near Broken Hill (New South Wales) as well as from the Devon's Cut in the East Pilbara Shire administrative area and the Shangri La Mine near Kununurra (Western Australia) in Australia; the Niujiaotang Cd-Zn deposit near Duyun (Guizhou) and the Guanmenshan Pb-Zn deposit near Fushun (Liaoning) in China; the Ohbuki Mine at Hinokage in Miyazaki Prefecture, Japan ; the Yana River basin near Verkhoyansk in the Siberian Republic of Sakha ( Yakutia ) in Russia and from the Reef Mine near Hartford in Cochise County of Arizona, from uranium prospecting on the Huron River in Baraga County of Michigan, the Sterling Mine near Sterling Hill in Sussex County of New Jersey and the Blanchard Mine near Bingham in Socorro County of New Mexico in the United States of America (USA) and near Mo Ba in the Vietnamese province of Thái Nguyên .

See also

literature

  • Otto Schneider: Preliminary note on some secondary minerals from Otavi (Deutsoh South-West Africa), including a new cadmium mineral . In: M. Bauer, E. Koken, Th. Liebisch (ed.): Centralblatt für Mineralogie, Geologie und Paläontologie in connection with the New Yearbook for Mineralogy, Geologle and Paläontologie . E. Schweizerbart'sche Verlagshandlung, Stuttgart 1906, p. 388–389 ( rruff.info [PDF; 344 kB ; accessed on June 23, 2018]).
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 572 (first edition: 1891).

Web links

Commons : Otavite  - collection of images, videos and audio files

Individual evidence

  1. 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.  287 .
  2. Webmineral - Otavite (English)
  3. a b c d e f Otavite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 63  kB ; accessed on June 23, 2018]).
  4. Otto Schneider: Preliminary note on some secondary minerals from Otavi (German South-West Africa), including a new cadmium mineral . In: M. Bauer, E. Koken, Th. Liebisch (ed.): Centralblatt für Mineralogie, Geologie und Paläontologie in connection with the New Yearbook for Mineralogy, Geologle and Paläontologie . E. Schweizerbart'sche Verlagshandlung, Stuttgart 1906, p. 388–389 ( rruff.info [PDF; 344 kB ; accessed on June 23, 2018]).
  5. Mineral Atlas: Otavit
  6. List of localities for Otavit in the Mineralienatlas and Mindat