Aheylite

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Aheylite
Aheylite-Cassiterite-rare08-2-01a.jpg
Aheylite (greenish, grape-like) and wavellite (yellowish, needle-like) on cassiterite (black) from the Huanuni mine, Pantaleón Dalence (Oruro) province , Bolivia ( overall size : 6.3 cm × 4.5 cm × 2.8 cm)
General and classification
other names

IMA 1984-036

chemical formula
  • FeAl 6 [(OH) 2 | PO 4 ] 4 • 4H 2 O
  • Fe 2+ Al 6 (PO 4 ) 4 (OH) 8 · 4H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DD.15 ( 8th edition : VII / D.15)
09/22/03/05
Similar minerals turquoise
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triklin-pedial; 1 or triclinic pinacoidal; 1
Space group P 1 (No. 1) or P 1 (No. 2)Template: room group / 1Template: room group / 2
Lattice parameters a  = 7.40  Å ; b  = 9.90 Å; c  = 7.63 Å
α  = 110.9 °; β  = 115.0 °; γ  = 70.0 °
Formula units Z  = 1
Physical Properties
Mohs hardness 5 to 5.5
Density (g / cm 3 ) measured: 2.84; calculated: 2.90
Cleavage no; perfect after {001}, good after {010}
Break ; Tenacity hooked, splintery; brittle
colour light blue to light green
Line color White
transparency transparent in thin flakes
shine Porcelain gloss to weak glass gloss

Aheylite is a very rare mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical formula FeAl 6 [(OH) 2 | PO 4 ] 4 · 4H 2 O and is therefore chemically a water-containing iron - aluminum - phosphate with additional hydroxide ions .

Aheylit crystallizes in the triclinic crystal system , but does not develop visible with the naked eye crystals (maximum crystal size about 3  microns ). Mostly it is found similar to its relative turquoise in the form of grape, kidney or spherical mineral aggregates up to about 5 mm in size as well as fine-fiber and intergrown masses.

Etymology and history

Was first discovered in the Aheylit named after the town mine Huanuni , one of the world's richest cassiterite - deposits in the Bolivian province Pantaleon Dalence . The mineral was first described scientifically in 1986 by Eugene E. Foord and Joseph E. Taggart, Jr., who named it in honor of Allen V. Heyl (1918-2008) after him.

classification

Since the aheylite was only recognized as an independent mineral in 1984 and this was only published in 1986, it is not yet listed in the 8th edition of the Strunz mineral classification, which has been outdated since 1977 . Only in the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , was the mineral given the system and mineral number. VII / D.15-30 . In the "lapis system" this corresponds to the class of "phosphates, arsenates and vanadates" and there the department "water-containing phosphates, with foreign anions ", where aheylite together with afmit , chalcosiderite , claraite , Faustite , kobokoboite , planerite and turquoise die "Turquoise Group" (VII / D.15) forms (as of 2018).

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also assigns aheylite to the category of “phosphates etc. with additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the other anions to the phosphate, arsenate or vanadate complex, so that the mineral is classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4  = 2: 1 “can be found where, together with chalcosiderite, Faustite, planerite and turquoise, the“ turquoise group ”with the system no. 8.DD.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns aheylite to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here it is also in the " turquoise group " with the system no. 42.09.03 within the subsection "Water-containing phosphates etc., with hydroxyl or halogen with (A) 3 (XO 4 ) 2 Z q × x (H 2 O)".

Crystal structure

Aheylite crystallizes triclinically in the space group P 1 (space group no. 1) or P 1 (no. 2) with the lattice parameters a  = 7.40  Å ; b  = 9.90 Å; c  = 7.63 Å; α = 110.9 °; β = 115.0 ° and γ = 70.0 ° as well as one formula unit per unit cell . Template: room group / 1Template: room group / 2

Education and Locations

Aheylite (light blue spherulites), cassiterite (black) and quartz (colorless) from the Huanuni mine, Bolivia (size: 3.5 cm × 2.3 cm × 0.8 cm)

Aheylite forms in the late stage of hydrothermal processes base metal - tin - deposits . As Begleitminerale occur among other cassiterite, pyrite , quartz , sphalerite , Variscit , Vivianit and Wavellite on.

In addition to its type locality mine Huanuni (Oruro), the mineral could also be found in Bolivia in the mine Tazna (also: Tasna) at Cerro Tazna in the mountainous region of Cordillera de Chichas (Potosí).

Other previously known sites are the prospecting called Bali Lo in the administrative area of Ashburton Shire in Western Australia, the "Les Montmins Mine" near Échassières in the French canton of Ébreuil (Allier) and the clay pit "Goonbarrow China" near Bugle in the English county of Cornwall .

See also

literature

  • Eugene E. Foord, Joseph E. Taggart, Jr .: A reexamination of the turquoise group: the mineral aheylite, planerite (redefined), turquoise and coeruleolactite . In: Mineralogical Magazine . tape 62 , 1998, pp. 93–111 (English, rruff.info [PDF; 1,2 MB ; accessed on April 27, 2020]).

Web links

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

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed April 27, 2020 .
  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.  503 (English).
  3. ↑ a b c d Aheylite . 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; 67  kB ; accessed on April 27, 2020]).
  4. ^ A b Eugene E. Foord, Joseph E. Taggart, Jr .: A reexamination of the turquoise group: the mineral aheylite, planerite (redefined), turquoise and coeruleolactite . In: Mineralogical Magazine . tape 62 , 1998, pp. 93–111 (English, rruff.info [PDF; 1,2 MB ; accessed on April 27, 2020]).
  5. ↑ Aheylite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 27, 2020 .
  6. ↑ Type locality Huanuni Mine, Huanuni, Dalence Province, Oruro Department, Bolivia. In: mindat.org. Hudson Institute of Mineralogy, accessed April 27, 2020 .
  7. ↑ 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 .
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 27, 2020 .
  9. ↑ Find location list for aheylite in the Mineralienatlas and Mindat , accessed on April 27, 2020.