Tiptopit

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Tiptopit
Tiptopite-82010.jpg
Colorless, needle-like tiptopite on brown roscherite from the type locality Tip Top Mine, South Dakota, USA (image width 3 mm)
General and classification
other names

IMA 1983-007

chemical formula K 2 (Na, Ca, □) 3 Li 3 Be 6 [4] [(OH) 2 | (PO 4 ) 6 ] · H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DA.25 ( 8th edition : VII / D.02)
06.22.11.01
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal-pyramidal; 6th
Space group P 6 3 (No. 173)Template: room group / 173
Lattice parameters a  = 11.65  Å ; c  = 4.69 Å
Formula units Z  = 1
Physical Properties
Mohs hardness 3.5
Density (g / cm 3 ) measured: 2.65 (2); calculated: 2.52
Cleavage no
Break ; Tenacity uneven; brittle
colour colorless
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.551
n ε  = 1.559
Birefringence δ = 0.008
Optical character uniaxial positive

Tiptopit is a very rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates". It crystallizes in the hexagonal crystal system with the chemical composition K 2 (Na, Ca, □) 3 Li 3 Be 6 [4] [(OH) 2 | (PO 4 ) 6 ] · H 2 O and is therefore chemically complex , water-containing phosphate with potassium , sodium or calcium , lithium and beryllium as well as hydroxide ions as additional anions . The elements sodium and calcium indicated in the first round brackets can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral. In addition, the square symbol □ indicates that this structural space is not fully occupied.

Tiptopit is colorless and usually develops needle-like crystals with a hexagonal base and a glass-like sheen on the surfaces, which are arranged in radial or tufted mineral aggregates .

Etymology and history

Tiptopit was first discovered in the "Tip Top Mine" near Fourmile about 8.5 kilometers southwest of Custer in the county of the same name in the US state of South Dakota and described in 1985 by Joel D. Grice , Donald R. Peacor , George W. Robinson , Jerry van Velthuizen , Willard L. Roberts , Thomas J. Campbell and Pete J. Dunn , who named the mineral after its type locality .

Type material of the mineral is in the Canadian Museum of Nature in Ottawa (Catalog No. 48833) in Canada as well as in the Geological Museum of the "South Dakota School of Mines and Technology" in Rapid City (Catalog No. 81-5102) and in the National Museum of Natural History in Washington, DC (Catalog No. 149609) in the United States.

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the tiptopite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "hydrous phosphates with foreign anions", where it was the only member of the unnamed group VII /D.02 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), also assigns the Tiptopit 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 , so that the mineral can be found according to its composition in the subsection “With small (and occasionally larger) cations”, where it is the only member of the unnamed group 8.DA.25 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Tiptopit to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he can be found as the only member of the unnamed group 42.06.11 within the subdivision “Water-containing phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q × x (H 2 O)”.

Crystal structure

Tiptopit crystallizes hexagonally in the space group P 6 3 (space group no. 173) with the lattice parameters a  = 11.65  Å and c  = 4.69 Å as well as one formula unit per unit cell . Template: room group / 173

Education and Locations

Tiptopite (colorless) on Montgomeryite (red) from the Tip Top Mine, South Dakota, USA (field of view 4 mm)

Tiptopite forms on the fracture surfaces of previously formed minerals in complex zoned granite - pegmatite . As accompanying minerals may include beryl , Englishit , Fransoletit , microcline , Montgomeryit , quartz and Roscherit occur.

In addition to its type locality "Tip Top Mine" in Custer County (South Dakota, USA), no other location for Tiptopit is known so far (as of 2018).

See also

literature

  • Joel D. Grice, Donald R. Peacor, George W. Robinson, Jerry van Velthuizen, Willard L. Roberts, Thomas J. Campbell, Pete J. Dunn: Tiptopite (Li, K, Na, Ca, □) 8 Be 6 ( PO 4 ) 6 (OH) 4 , a new mineral species from the Black Hills, South Dakota . In: The Canadian Mineralogist . tape 23 , 1985, pp. 43–46 ( rruff.info [PDF; 687 kB ; accessed on February 1, 2018]).
  • Donald R. Peacor, Roland C. Rouse, Jung-Ho Ahn: Crystal structure of tiptopite, a framework beryllophosphate isotypic with basic cancrinite . In: American Mineralogist . tape 72 , 1987, pp. 816–820 ( rruff.info [PDF; 774 kB ; accessed on February 1, 2018]).

Web links

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

Individual evidence

  1. ↑ a b c d e 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.  494 .
  2. ↑ Webmineral - Tiptopite
  3. ↑ 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 .
  4. ↑ a b Tiptopite . 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 February 1, 2018]).
  5. ↑ a b Mindat - Tiptopite
  6. ↑ Joel D. Grice, Donald R. Peacor, George W. Robinson, Jerry van Velthuizen, Willard L. Roberts, Thomas J. Campbell, Pete J. Dunn: Tiptopite (Li, K, Na, Ca, □) 8 Be 6 (PO 4 ) 6 (OH) 4 , a new mineral species from the Black Hills, South Dakota . In: The Canadian Mineralogist . tape 23 , 1985, pp. 43–46 ( rruff.info [PDF; 687 kB ; accessed on February 1, 2018]).
  7. ↑ Find location list for Tiptopit in the Mineralienatlas and Mindat