Warwickit

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Warwickit
Warwickite-616477.jpg
Needle-shaped warwickite (brown) from the Nuestra Señora del Carmen mines, La Celia , Jumilla , Murcia, Spain
General and classification
other names

Enceladit

chemical formula
  • Mg (Mg 0.5 Ti 0.5 ) [O | BO 3 ]
  • (Mg, Ti, Fe, Cr, Al) 2 O (BO 3 )
Mineral class
(and possibly department) 		Borates (formerly carbonates, nitrates and borates)
System no. to Strunz
and to Dana 		6.AB.20 ( 8th edition : V / G.03)
02.25.02.02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pnam (No. 62, position 6)Template: room group / 62.6
Lattice parameters a  = 9.20  Å ; b  = 9.36 Å; c  = 3.09 Å
Formula units Z  = 4
Frequent crystal faces {010}, {100}, {110}, {130}, {310}
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 3.34 to 3.36; calculated: 3.40
Cleavage good after {100}
Break ; Tenacity uneven; brittle
colour dark brown to black, dark yellow, light brown to reddish brown
Line color bluish black
transparency opaque, transparent on the thinnest edges
shine weak glass luster, pearlescent luster, weak metallic luster on cleavage surfaces
Crystal optics
Refractive indices n α  = 1.806
n β  = 1.809
n γ  = 1.830
Birefringence δ = 0.024
Optical character biaxial positive
Pleochroism Visible: X = yellowish brown; Y = reddish brown; Z = cinnamon brown
Other properties
Chemical behavior easily soluble in sulfuric acid (H 2 SO 4 )

Warwickite is a rarely occurring mineral from the mineral class of the " borates ". It crystallizes in the orthorhombic crystal system with the chemical composition Mg (Mg 0.5 Ti 0.5 ) [O | BO 3 ] and is therefore a magnesium borate with additional oxygen ions .

In natural warwickite samples, part of the magnesium is usually replaced ( substituted ) by titanium , which is expressed by the elements given in round brackets. In more recent analyzes, however, it was found that in addition to titanium, the magnesium can also be partially replaced by triple positively charged iron ions , chromium and / or aluminum , which is why the formula is now with (Mg, Ti, Fe 3+ , Cr, Al) 2 O BO 3 ) is specified.

The mineral develops short to long prismatic, rounded crystals , but is also found in the form of irregular grains up to about five millimeters in diameter. The crystals are predominantly opaque, but the thinnest edges can also be transparent. The surfaces show a weak glass luster (with irregular surfaces also pearlescent) and a weak metallic luster on gap surfaces . Due to the various foreign admixtures , the color of Warwickite varies from dark brown to black, dark yellow and light brown to reddish brown. His line color , on the other hand, is bluish black throughout.

Etymology and history

Dark gray, rounded Warwickite crystals in a matrix from Amity near Warwick , Orange County, New York, USA (size: 14.5 cm × 11.0 cm × 5.5 cm)

Warwickite was first discovered near the small town of Warwick in Orange County in the US state of New York and described in 1838 by Charles Upham Shepard , who named the mineral after its type locality .

Enceladit is a synonym that is no longer used today. In 1846 Thomas Sterry Hunt analyzed some mineral samples from the type locality of Warwickite, considered the material to be a new type of mineral and named it after the giant Enkelados from Greek mythology . However, it later turned out that the material was an impure variety of the previously found warwickite.

Type material of the mineral is kept in the Natural History Museum in Paris , France (Catalog No. 74217, 99697) and the National Museum of Natural History in Washington, DC , USA (Catalog No. 128712).

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the warwickite still belonged to the common mineral class of the "carbonates, nitrates and borates" and there to the department of the "island borates", where together with pinakiolite the "warwickite pinakiolite" Group "with the system no. V / G.03 and the other members Aluminomagnesiohulsit , hulsite , Magnesiohulsit , Pertsevit and Yuanfuliit formed.

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 Warwickit to the now independent class of "borates" and there in the department of "monoborates". This is further subdivided according to the type of borate complex and the possible presence of further anions , so that the mineral is classified in the sub-section “BO 3 with additional anions; 1 (Δ) + OH etc. ”can be found where the“ Warwickit group ”with the system no. 6.AB.20 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , classifies Warwickit as the outdated Strunz'sche systematics in the common class of "carbonates, nitrates and borates" and there in the department of "anhydrous borates". Here it can be found together with Yuanfuliit in the unnamed group 02/24/02 within the sub-section “Anhydrous borates with (A) 2+ BO 2 [XO 3 ]”.

Crystal structure

Warwickite crystallizes orthorhombically in the space group Pnam (space group no. 62, position 6) with the lattice parameters a  = 9.20  Å ; b  = 9.36 Å and c  = 3.09 Å as well as 4 formula units per unit cell . Template: room group / 62.6

Education and Locations

Warwickite forms as a accessory constituent in limestone and associated skarns represented by boron - Metasomase were converted partially. It can also arise in lamproic rocks that are penetrated by carbonatite-like veins . As Begleitminerale occur among other apatite , Chondrodite , diopside , Dravit , fluorite , graphite , ilmenite , magnetite , pyrite , pyrrhotite , Sinhalit , scapolite , spinel , Szaibélyit and titanite on.

As a rare mineral formation, Warwickite could only be detected at a few sites, with around 15 sites being known to date (as of 2015). In addition to its type locality Warwick and the nearby towns of Amity and Edenville in Orange County , the mineral in the US state of New York was also found in the Edwards Mine in the Balmat-Edwards Zinc Region in St. Lawrence County . Otherwise Warwickit was only found in the United States in the "Edison-Bodnar" quarries near Rudeville in Sussex County of New Jersey.

The only known site in Germany so far is Ilfeld in the Thuringian district of Nordhausen .

Other well-known sites include the Mount Heemskirk mineral field in the Zeehan District on the Australian island of Tasmania , the village of Herschel in Hastings County in the Canadian province of Ontario , the Neichi mine near Kamineichi near Miyako (Iwate) on the Japanese island of Honshū, the Kvæfjord in the Norwegian province of Troms, the Aldan highlands in Eastern Siberia and the Chelyabinsk Oblast in the Urals in Russia as well as the “La Aljorra” quarries near Cartagena in the Spanish region of Murcia .

See also

literature

Web links

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

Individual evidence

  1. ↑ 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.  331 .
  2. ↑ a b IMA / CNMNC List of Mineral Names. September 2014 (PDF; 1.5 MB; p. 187).
  3. ↑ a b c d e f g h Warwickite , 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).
  4. ↑ a b c Mindat - Warwickite .
  5. ^ Mineral Atlas: Warwickite
  6. ↑ 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 .
  7. ^ William Crookes: Chemical News and Journal of Industrial Science. Volume 30, London 1874 Limited preview in Google Book search.
  8. ↑ James Douglas: A Memoir of Thomas Sterry Hunt, MD, Ll.D. (Cantab.) MacCalla & Company Inc Press, Philadelphia 1898, p. 8 ( Text Archive - Internet Archive )
  9. ↑ Mindat - Number of localities for Warwickit .
  10. ↑ Find location list for Warwickite at the Mineralienatlas and at Mindat .