Zinc melanterite

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Zinc melanterite
General and classification
other names
  • Sommairit
  • Zinc melanterite
chemical formula
  • Zn [SO 4 ] • 7H 2 O
  • (Zn, Fe 2+ ) [SO 4 ] • 7H 2 O
  • (Zn, Cu, Fe 2+ ) [SO 4 ] • 7H 2 O
Mineral class
(and possibly department) 		Sulphates (selenates, tellurates, chromates, molybdates and tungstates)
System no. to Strunz
and to Dana 		7.CB.35 ( 8th edition : VI / C.06)
06/29/10/03
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / c (No. 14)Template: room group / 14
Lattice parameters a  = 13.88  Å ; b  = 6.39 Å; c  = 11.39 Å
β  = 102.1 °
Formula units Z  = 4
Physical Properties
Mohs hardness 2 to 2.5
Density (g / cm 3 ) measured: 2.02-2.03; calculated: 1.93
Cleavage is missing
Break ; Tenacity uneven
colour yellowish green, greenish blue to apple green, very light greenish blue in transmitted light
Line color White
transparency transparent to translucent
shine Glass gloss, resin gloss
Crystal optics
Refractive indices n α  = 1.477 to 1.479
n β  = 1.483 to 1.487
n γ  = 1.488 to 1.489
Birefringence δ = 0.011
Optical character biaxial positive

Zinc melanterite is a very rarely occurring mineral from the mineral class of "sulfates (and relatives, see classification )" with the idealized chemical composition Zn [SO 4 ] · 7H 2 O and is therefore chemically a water-containing zinc sulfate , more precisely its heptahydrate. Since naturally occurring zinc melanterites usually have a small amount of zinc replaced (substituted) by iron (Fe 2+ ) and / or copper (Cu) , the formula is also used in various sources with (Zn, Fe 2+ ) [SO 4 ] · 7H 2 O or with (Zn, Cu, Fe 2+ ) [SO 4 ] · 7H 2 O indicated. In order to be classified as zinc melanterite, however, zinc must always be the main component in the compound.

Zinc melanterite crystallizes in the monoclinic crystal system and develops short prismatic crystals up to about 1.88 mm in size with a resin to glass-like gloss on the surfaces, but can also be found in the form of stalactites , crusty coatings or granular to massive mineral aggregates . The transparent to translucent crystals are yellowish green to apple green or greenish blue in color and appear very light greenish blue in transmitted light. The line color of zinc melanterite, on the other hand, is white.

Etymology and history

Zinc melanterite was first discovered in the summer of 1916 by Esper S. Larsen in the Good Hope Mine near the town of Vulcan in Gunnison County in the US state of Colorado. The mineral was first described in 1920 by Larsen and ML Glenn, who first proposed the name zinc-copper-melanterite due to its main chemical component zinc, the likewise relevant content of copper and its relationship to melanterite . According to their analyzes, the cation fraction (R) consists mainly of Zn and Cu, with Zn predominating in molecular terms. In the first description, the oxide formula is generally given as RO · SO 3 · 7H 2 O or more precisely as (Zn, Cu, Fe) O · SO 3 · 7H 2 O with a molar ratio of Zn: Cu: Fe = 100: 98: 19 . Larsen and Glenn limit the composition for a zinc melanterite to the effect that the molecular ratio of ZnO to CuO should be greater than 3: 1.

A new analysis by Tiegeng Liu, Guohong Gong, Lin Ye 1995 on two samples from Lüeyang ( Leh-Yang ) in the south of the Chinese province of Shaanxi , on the other hand, showed a composition of 16.07 to 16.63% ZnO and 8.41 to 9.30 % FeO. The proportion of CuO was below 0.01%. Tiegeng Liu, Guohong Gong and Lin Ye therefore corrected the idealized chemical formula for zinc melanterite to (Zn, Fe) SO 4 · 7H 2 O.

Zinc melanterite was first described before the International Mineralogical Association (IMA) was founded and the mineral was mostly recognized in the professional world, even if it is listed in the mineralogical tables by Strunz and Tennyson in 1982 as a mixed crystal within the melanterite series.

As a so-called grandfathered mineral , recognition as an independent mineral type was adopted by the Commission on new Minerals, Nomenclature and Classification (CNMNC). The two-word name zinc melanterite was, however, adjusted with the publication “Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical marks” in 2008 and the mineral was renamed zinc melanterite ( renamed , Rn).

The type material of the mineral is in the National Museum of Natural History in Washington, DC, USA under the catalog no. 93244 kept.

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , zinc melanterite belonged to the mineral class of "sulfates, chromates, molybdates, tungstates (including selenates and tellurates)" and there to the department "C. Water-containing sulfates, without foreign anions ”, where together with alpersite , bieberite , boothite , mallardite and melanterite the“ melanterite group ”with the system no. VI / C.06 .

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 zinc melanterite in the category of "sulfates (selenates, etc.) without additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved , so that the mineral is classified in the subdivision “B. With only medium-sized cations ”is to be found, where the“ melanterite group ”with the system number is also found together with alpersite, bieberite, boothite, mallardite and melanterite. 7.CB.35 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns zinc melanterite to the class of "sulfates, chromates and molybdates" and there in the department of "water-containing acids and sulfates". Here it is also in the " melanterite group (heptahydrate, monoclinic: P 2 1 / c ) " with the system no. June 29, 2010 to be found in the subsection “Water-based acids and sulfates with AXO 4 × x (H 2 O)”.

Crystal structure

Zinc melanterite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 13.88  Å ; b  = 6.39 Å; c  = 11.39 Å and β = 102.1 ° as well as 4 formula units per unit cell . Template: room group / 14

properties

Like all water-containing sulfates, zinc melanterite dehydrates quickly in air.

Modifications and varieties

The compound Zn [SO 4 ] · 7H 2 O is dimorphic and, in addition to the monoclinically crystallizing zinc melanterite, also occurs as orthorhombically crystallizing goslarite .

Education and Locations

Zinkmelanterit formed in the oxidation zone of pyritic ore - deposits . In addition to this, sphalerite and chalcopyrite appear as accompanying minerals .

As a very rare mineral formation, zinc melanterite is only known in a few samples from less than 10 sites (as of 2018). In addition to its type locality Good Hope Mine and the nearby Vulcan Mine in Colorado, the mineral occurred in the United States of America in the Santa Rosa Mine at Malpais Mesa in the Inyo Mountains in the county of California and at Santa Rita in Grant County of New Mexico on.

Zinc melanterite was also found near Lüeyang in the Chinese province of Shaanxi, in the Kamariza mines near Agios Konstantinos and in the Lavrio mining area in the Greek region of Attica, in the Sar Cheshmeh open-cast mine near Rafsanjan in the Iranian province of Kerman and in the Johkoku mine near Kaminokuni on the Japanese Oshima (Hokkaidō) peninsula .

Another possible find in the Santa Elena Mine near Calingasta in the Argentine province of San Juan has not yet been confirmed.

See also

literature

  • Esper S. Larsen, ML Glenn: American Journal of Science . tape 50 , 1920, p. 225–233 ( rruff.info [PDF; 622 kB ; accessed on April 20, 2018]).
  • Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 612 .
  • Tiegeng Liu, Guohong Gong, Lin Ye: Discovery and investigation of zinc-melanterite in nature . In: Acta Mineralogica Sinica . tape 15 , no. 3 , 1995, p. 286–290 (Chinese, brief description in English).
  • John L. Jambor, Edward S. Grew, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape 81 , no. 11-12 , 1996, pp. 1513–1518 ( minsocam.org [PDF; 541 kB ; Retrieved April 19, 2018] New Data. Zinc-melanterite , p. 1518).

Web links

Individual evidence

  1. ^ A b c Karl Hugo Strunz , Christel Tennyson : Mineralogical tables . 8th edition. Academic publishing company Geest & Portig KG, Leipzig 1982, p.  283 .
  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.  384 .
  3. ↑ a b c IMA / CNMNC List of Mineral Names; November 2017 (PDF 1.67 MB)
  4. ↑ a b 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 .
  5. ↑ a b c d e Zincmelanterite . 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; 66  kB ; accessed on April 17, 2018]).
  6. ↑ a b c Webmineral - Zincmelanterite
  7. ↑ a b c d Mindat - Zincmelanterite
  8. ^ Esper S. Larsen, ML Glenn: American Journal of Science . tape 50 , 1920, p. 226 ( rruff.info [PDF; 622 kB ; accessed on April 20, 2018]).
  9. ↑ John L. Jambor, Edward S. Grew, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape 81 , no. 11-12 , 1996, pp. 1513–1518 ( minsocam.org [PDF; 541 kB ; Retrieved April 19, 2018] New Data. Zinc-melanterite , p. 1518).
  10. ↑ C. Palache, H. Berman, C. Frondel (Eds.): The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Edition = 7th, revised and expanded . tape 2 . John Wiley and Sons, New York 1951, p. 508 .
  11. ^ Ernst AJ Burke: Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical marks . In: The Mineralogical Record . tape 39 , no. 2 (March – April), 2008 ( edu.au [PDF; 2.8 MB ; accessed on April 23, 2018]).
  12. ↑ Catalog of Type Mineral Specimens - Z. (PDF 30 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
  13. ↑ Mindat– Number of localities for zincmelanterite
  14. ↑ a b c List of places where zinc melanterite was found in the Mineralienatlas and Mindat