Painite

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Painite
Painite-266170.jpg
Dark purple painite crystal from Mogok, Sagaing District, Myanmar
General and classification
chemical formula CaZrAl 9 [O 15 | BO 3 ]
Mineral class
(and possibly department) 		Borates (formerly "Carbonates, Nitrates and Borates")
System no. to Strunz
and to Dana 		6.AB.85 ( 8th edition : V / G.05)
07.05.02.01
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal dipyramidal; 6 / m
Room group (no.) P 6 3 (No. 173)
Lattice parameters a  = 8.72  Å ; c  = 8.47 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 8th
Density (g / cm 3 ) 4th
Cleavage no
colour red, orange-red, brownish
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.816
n ε  = 1.788
Birefringence δ = 0.028
Optical character uniaxial negative
Pleochroism strong dichroism; red-brown-orange

Painite is a very rare mineral from the mineral class of " borates " (formerly "carbonates, nitrates and borates", see classification ). It crystallizes in the hexagonal crystal system with the chemical composition CaZrAl 9 [O 15 | BO 3 ] and develops hexagonal, prismatic to needle-like crystals in red, orange-red or brownish color. Color-giving foreign additions are chromium , vanadium and iron .

Etymology and history

Painite was first discovered at Ongaing , near the city of Mogok in the Mandalay region of Myanmar (formerly Burma ) and described in 1957 by Claringbull, Hey and Payne, who named the mineral after Arthur Charles Davy Pain (1901-1971), a British mineralogist and Gemologists named.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the painite belonged to the common mineral class of "carbonates, nitrates and borates " and there to the department of "island borates", where it forms an independent group with fluoborite , jeremejewite and karlite educated.

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 painite to the new class of "borates" and there into the department of "monoborates". This section is, however, further subdivided according to the structure of the borate complex and the possible presence of further anions , so that the mineral according to its composition in the sub-section “BO 3 with additional anions; 1 (Δ) + OH etc. ”can be found, where it is the only member of the unnamed group 6.AB.85 .

In contrast to Strunz's systematics, the systematics of minerals according to Dana , which is mainly used in the English-speaking world, assigns painite to the class of " oxides and hydroxides " and there in the department of "multiple oxides". Here he is to be found as the only member of the unnamed group 05/07/02 within the subdivision of " Multiple oxides with the formula ABX 2 ".

Crystal structure

Painite crystallizes hexagonally in the space group P 6 3 (space group no. 173) with the lattice parameters a  = 8.72  Å and c  = 8.47 Å and 2 formula units per unit cell .

properties

The colors of the painite crystals range from brown (sometimes with a strong greenish tinge) through reddish brown to red (in all brightnesses from clear to almost black). Some pieces are also light purple to pink. Some pieces, especially the radial aggregates, show clear zoning. Painite is strongly dichroic . About twins of Painite nothing has so far been published clearly, even though some pieces have been observed with regular adhesions, including a copy with right angles overgrown crystals . Here, however, it remains to be seen whether there are actually twins.

Some of the painites (proportion unknown up to now) show a color change from brown in daylight to red-brown in incandescent light. This color change, which is already very clearly recognizable, has so far been classified as too small by the only investigating body to be recognized. This is incomprehensible, however, since these pieces show a clear, pale greenish brown in daylight (sun) and a clear pink without brown spots in lamplight (limonite inclusions are disturbing, clear pieces are necessary for observation). The color change is complete and easy to see.

Education and Locations

Large, dark purple painite crystal interspersed with small, light red rubies from Mogok, Sagaing District, Myanmar

The mineral was discovered in Burma (now Myanmar ) in the early 1950s . Before 2001, only 3 crystals with a combined weight of less than 3.5 grams were known. A maximum of 14 more specimens were found between 2001 and 2004. In 2005 one of the primary deposits was found in Ongaing and later the richer deposit in Wetloo (Wet Luu). Several thousand specimens with an individual weight of up to over 500 grams have now been found. Most of the pieces are cracked or interspersed with limonite or ruby . Pieces with end faces or clear sandable specimens are still very rare.

Most of them are pieces from the heavily weathered layer near the surface. The pieces are then often interspersed with limonite . Painite itself is extremely weather-resistant, but the cracks quickly fill up with the brown mineral. Furthermore, many painites are associated with ruby, or even converted into ruby ​​due to the similar composition (painite has a very high aluminum oxide content).

Apart from its type locality Ongaing and Wetloo, the mineral could only be found at Nanyazeik in the Myitkyina district in Kachin State .

Use as a gem stone

faceted painite including the representation of the color change from olive green-brown in daylight to red-brown under warm artificial light, 0.86ct, found in the Thurein Taung Mine in Mogok Myanmar (Burma)

Due to its extreme rarity and good physical properties , Painite is sometimes processed into valuable gemstones or, due to the high demand from mineral collectors, especially mined for collection purposes and exported as raw pieces. Other uses are not known.

See also

Web links

Commons : Painit  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 334 .
  2. ↑ a b c Painite at mindat.org (engl.)