Archerite

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Archerite
Biphosphammite & Archerite.jpg
Archerite (white) and bisphosphammite (brown) from Murra-el-Elevyn Cave , Dundas Shire , Australia
General and classification
other names

IMA 1975-008

chemical formula
  • KH 2 (PO 4 )
  • (K, NH 4 ) H 2 PO 4
  • (K, NH 4 ) [PO 2 (OH) 2 ]
  • K [PO 2 (OH) 2 ]
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.AD.15
01.37.04.02
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol tetragonal-scalenohedral; 4 2 m
Space group I 4 2 d (No. 122)Template: room group / 122
Lattice parameters a  = 7.45  Å ; c  = 6.98 Å
Formula units Z  = 4
Physical Properties
Mohs hardness 1 to 2
Density (g / cm 3 ) measured: 2.23; calculated: 2.34
Cleavage is missing
colour white to beige-white, brownish-yellow to colorless
Line color White
transparency translucent
shine weak glass sheen, wax sheen, greasy sheen
Crystal optics
Refractive indices n ω  = 1.511 to 1.513
n ε  = 1.468 to 1.470
Birefringence δ = 0.043
Optical character uniaxial negative
Other properties
Chemical behavior water soluble

Archerite is a very rare mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical composition K [PO 2 (OH) 2 ] or KH 2 (PO 4 ) and is therefore chemically a basic potassium phosphate .

Archerit crystallizes in the tetragonal crystal system and develops prismatic-pyramidal crystals up to about two millimeters in size with a weak, glass-like sheen on the surfaces. But it can also be found in the form of crusty coatings.

In its pure form, archerite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also be translucent white to beige-white and take on a brownish-yellow color due to foreign admixtures. With a Mohs hardness of 1 to 2, archerite is one of the soft minerals that, like the reference minerals talc (hardness 1) and plaster of paris (hardness 2), can be scratched with the fingernail.

Etymology and history

Even before it was discovered as a natural mineral formation, the compound KH 2 (PO 4 ) was known as a synthetic product, first investigated by O. Hasse in 1925 and described in 1930 by J. West as potassium dihydrogen phosphate . The crystal structure was analyzed by SB Hendricks.

Archerit was first discovered in the Petrogale Cave near a rest stop near Madura in Western Australia. It was first described in 1977 by Peter J. Bridge , who named the mineral after Michael Archer (* 1945), curator for mammals at the Queensland Museum . He had discovered the Petrogale Cave and collected samples in which the new mineral was discovered.

The type material of the mineral is in the Western Australian Museum (WAM) in Perth , Australia under the catalog no. MDC 5901 kept.

classification

Archerit is not yet listed in the outdated 8th edition of the Strunz mineral classification . Only in the last revised and updated "Lapis mineral directory" in 2018, which is still based on this classic system of Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral received the system and mineral no. VII / A.12-50 . In the "Lapis Classification", this corresponds to the department of "Anhydrous Phosphate [PO 4 ] 3- , without foreign anions " where Archerit with Bario Olgit , Biphosphammit , Buchwaldit , Iwateit , Monetit , Nahpoit , Olgit , Phosphammit , Svenekit and Weilit forms an independent but unnamed group.

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 the archerite to the category of “phosphates etc. without additional anions; without H 2 O “. This is, however, further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the subsection “With only large cations”, where it only forms the unnamed group 8.AD.15 together with bisphosphammite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the archerite to the class of "phosphates, arsenates and vanadates" and there in the department of "phosphate minerals". Here it can be found together with bisphosphammite in the unnamed group 37.01.04 within the sub-section “Anhydrous acid phosphates etc., with various formulas”.

Chemism

The idealized, theoretical composition of Archerite (KH 2 (PO 4 ) consists of 28.73% by weight of potassium  (K), 1.48% by weight of hydrogen  (H), 22.76% by weight of phosphorus  (P ) and 47.03% by weight oxygen  (O). Since archerite usually occurs in close association with bisphosphammite, a small proportion of the potassium is often replaced ( substituted ) by ammonium (NH 4 ). Therefore, the formula for archerite is used in different Sources also indicated with (K, NH 4 ) H 2 PO 4 or (K, NH 4 ) [PO 2 (OH) 2 ].

Crystal structure

Archerit crystallizes tetragonally in the space group I 4 2 d (space group no. 122) with the lattice parameters a  = 7.45  Å and c  = 6.98 Å as well as four formula units per unit cell . Template: room group / 122

Education and Locations

At its type locality , the Petrogale Cave in Western Australia, archerite formed as a component of stalactites and crusts on the cave walls from bat guano , i.e. from the excrement of bats through the action on limestone . As Begleitminerale occur among other Aphthitalit , Biphosphammit , calcite , guanine , halite , Mundrabillait , Newberyit , Oxammit , Stercorit , syngenite , weddellite and Whitlockit on.

Archerite is one of the very rare mineral formations and has so far only been discovered in a few samples from less than 10 sites. In Australia, apart from the Petrogale Cave, the mineral could only be found in the nearby Murra-el-elevyn and Cocklebiddy caves near the rest stop of the same name in the administrative area of Dundas Shire .

Other previously known sites are the San Salvador Cave on the island of the same name on the northeastern edge of the Bahamas , the Arnhem Cave in the Namibian region of Khomas, the Hibashi Cave in the Saudi Arabian province of Mecca ( Mintaqah Makkah ) and in the Kahf -Kharrat Najem Cave in the Emirate of Fujairah ( Fujairah ) in the United Arab Emirates.

See also

literature

  • J. West: XXVI. a quantitative X-ray analysis of the structure of potassium dihydrogen phosphate (KH 2 PO 4 ) . In: Journal of Crystallography . tape 74 , 1930, pp. 306–332 (English, available online at rruff.info [PDF; 11.4 MB ; accessed on April 28, 2019]).
  • PJ Bridge: Archerite, (K, NH 4 ) H 2 PO 4 , a new mineral from Madura, Western Australia . In: Mineralogical Magazine . tape 41 , 1977, pp. 33–35 (English, available online at rruff.info [PDF; 167 kB ; accessed on April 21, 2019]).
  • Michael Fleischer , Adolf Pabst , Joseph Anthony Mandarino , George Y. Chao: New mineral names . In: American Mineralogist . tape 62 , 1977, pp. 1057–1061 (English, available online at rruff.info [PDF; 668 kB ; accessed on April 26, 2019]).

Web links

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

Individual evidence

  1. ↑ a b c Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2019, accessed April 25, 2019 .
  2. ↑ a b Yasuhiro Ono, Noboru Yamada, Tomoyuki Hikita: Structure Refinements of the Mixed Crystal K 0.78 (NH 4 ) 00:22 H 2 PO 4 in the Temperature Range from 20 K to 250 K . In: Journal of the Physical Society of Japan . tape 60 , no. 8 , August 1991, p. 2673-2677 , doi : 10.1143 / JPSJ.60.2673 (English).
  3. ↑ a b c d e Stefan Weiss: The great 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 .
  4. ↑ 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.  435 (English).
  5. ↑ David Barthelmy: Archerite Mineral Data. In: webmineral.com. Accessed April 20, 2019 .
  6. ↑ a b c d e f Archerite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 25, 2019 .
  7. ↑ a b c d Archerite . 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; 434  kB ; accessed on April 25, 2019]).
  8. ^ J. West: XXVI. a quantitative X-ray analysis of the structure of potassium dihydrogen phosphate (KH 2 PO 4 ) . In: Journal of Crystallography . tape 74 , 1930, pp. 306–332 (English, available online at rruff.info [PDF; 11.4 MB ; accessed on April 28, 2019]).
  9. ↑ 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. 698-699 .
  10. ^ Catalog of Type Mineral Specimens - Archerite. (PDF 84 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed April 25, 2019 .
  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 April 25, 2019 .
  12. ↑ PJ Bridge: Archerite, (K, NH 4 ) H 2 PO 4 , a new mineral from Madura, Western Australia . In: Mineralogical Magazine . tape 41 , 1977, pp. 33–35 (English, available online at rruff.info [PDF; 167 kB ; accessed on April 21, 2019]).
  13. ↑ Localities for Archerite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 25, 2019 .
  14. ↑ Find location list for Archerite at the Mineralienatlas and at Mindat