Putnisite
| Putnisite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 2011-106 |
| chemical formula | SrCa 4 Cr 3+ 8 (CO 3 ) 8 SO 4 (OH) 16 · 25 H 2 O |
|
Mineral class (and possibly department) |
Carbonates and nitrates (according to Weiß, Lapis mineral directory) |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pnma (No. 62) |
| Lattice parameters | a = 15.351 (3) Å ; b = 20.421 (4) Å; c = 18.270 (4) Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 1.5 to 2 |
| Density (g / cm 3 ) | measured: 2.20 (3); calculated: 2.23 |
| Cleavage | perfect according to {100}, good according to {010} and {001} |
| Break ; Tenacity | uneven; brittle |
| colour | violet |
| Line color | pink |
| transparency | translucent |
| shine | Wax gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.552 (3) n β = 1.583 (3) n γ = 1.599 (3) |
| Optical character | biaxial negative |
| Pleochroism | clear: X = light blue gray Y = Z = light purple |
Putnisite is a very rare mineral with the chemical composition SrCa 4 Cr 3+ 8 (CO 3 ) 8 SO 4 (OH) 16 · 25H 2 O and is therefore chemically a water-containing strontium - calcium - chromium sulfate carbonate with additional Hydroxide ions .
Putnisite is translucent and only develops small, pseudo- cubic crystals up to about 0.5 millimeters in size with a purple color and a wax-like sheen on the surfaces. Putnisite leaves a pink line on the whiteboard .
Etymology and history
Putnisite was first discovered in 2011 during mine work on the “Polar Bear” peninsula on Lake Cowan near the town of Norseman in Western Australia . The mineral was scientifically described and published in 2014 by Peter Elliott , Gerald Giester, Ralph Rowe and Allan Pring, who named it after the Australian mineralogists Andrew and Christine Putnis, because of their outstanding contributions to mineralogy, in particular the phase transformation of minerals and mineral surface science (before all crystal growth and dissolution processes).
Type material of the mineral is kept in the collection of the South Australian Museum in Adelaide (catalog number G33429 ) and the Canadian Museum of Nature in Ottawa (catalog number CMNMC 86133 ).
classification
Putnisite was only recognized as an independent mineral by the IMA in 2012 and published in 2014. An exact group assignment in the 9th edition of the Strunz'schen mineral systematics , the last update of which was carried out with the publication of the IMA list of mineral names in 2009, is therefore not yet known.
Only in the "Lapis mineral directory", which, out of consideration for private collectors and institutional collections, is still based on the classical systematics of Karl Hugo Strunz in the 8th edition , the mineral received the system no. V / E.3-100 . According to this classification, the mineral would be a member of the “hydrotalcite group” (V / E.03) within the division of “water-containing carbonates with foreign anions ”.
Crystal structure
Putnisite crystallizes in the orthorhombic crystal system in the space group Pnma (space group no.62 ) with the lattice parameters a = 15.351 (3) Å , b = 20.421 (4) Å and c = 18.270 (4) Å as well as 4 formula units per unit cell . The volume of the unit cell is V = 5727 (2) Å 3 .
The crystal structure of putnisite consists of a complex network that has not yet been observed in other minerals or synthetic compounds. Eight Cr 3+ ions are coordinated with hydroxide ions (OH - ) and carbonate oxygen atoms (CO 3 2− ) to form coordination cahedrons, which are connected by their edges to form a symmetrical and flat ring, with the Sr 2 in their centers + Cations lie. Two of the free corners of these octahedra are linked to one another via triangles made of CO 3 , four of the triangles being aligned in the positive direction and four in the negative direction of the a -axis.
Four of the ring structures made of Cr octahedra are linked parallel to the b and c axes via four Ca 2+ ions, one carbonate group bridging two Cr atoms with one Ca atom. The other coordination points of the Ca atoms are occupied by water molecules and thus additionally hold the crystal lattice together through hydrogen bonds . This results in layers similar to a checkerboard pattern, which are stacked perpendicular to the a -axis. The crystal water contained is stored between the layers. In the cavities that are created by the four Ca atoms, there are free OH - ions. The Sr 2+ ions span a doubly widened antiprism (16 faces), whereby two opposing Sr atoms are bridged by a sulfate group (SO 4 2− ) in the direction of the a -axis. This coordination creates a three-dimensional network from the Ca-bridged layers of octahedral Cr rings.
Education and Locations
Putnisite forms in volcanic rock . At its type locality , the “Polar Bear” peninsula, it appeared in a matrix of quartz and amorphous , chromium-containing silicate rock .
The only other location so far is the Armstrong Mine about 30 km southwest of Kambalda ( Coolgardie Shire ) in Western Australia.
See also
literature
- P. Elliott, G. Giester, R. Rowe, A. Pring: Putnisite, SrCa 4 Cr 8 3+ (CO 3 ) 8 SO 4 (OH) 16 · 25H 2 O, a new mineral from Western Australia: description and crystal structure . In: Mineralogical Magazine . tape 78 , no. 1 , 2014, p. 131–144 , doi : 10.1180 / minmag.2014.078.1.10 (English).
- Williams PA, Hatert F., Pasero M., Mills SJ: CNMNC Newsletter No. June 13, 2012 - New minerals and nomenclature modifications approved in 2012 . In: Mineralogical Magazine . tape 76 , no. 3 , June 2012, p. 807-817 ( cnmnc.main.jp [PDF; 114 kB ; Retrieved May 10, 2018] Peter Elliott, Gerald Giester, Ralph Rowe, and Allan Pring: Putnisite, IMA 2011-106. , P. 810).
- Peter Elliott, Gerald Giester, Ralph Rowe and Allan Pring: Putnisite, SrCa 4 Cr 3+ 8 (CO 3 ) 8 SO 4 (OH) 16 · 25H 2 O, a new mineral from Western Australia: description and crystal structure . In: Mineralogical Magazine . tape 78 , 2014, p. 131–144 , doi : 10.1180 / minmag.2014.078.1.10 .
Web links
- Mineral Atlas: Putnisite
- Lars Fischer: loners from rings and layers. Spektrum.de , April 23, 2014, accessed on September 5, 2019 .
- Natali Anderson: Putnisite: New Mineral Discovered in Australia. In: sci-news.com. Sci-News, April 22, 2014, accessed on September 5, 2019 .
Individual evidence
- ↑ a b c d e f g h i j k l Peter Elliott, Gerald Giester, Ralph Rowe and Allan Pring: Putnisite, SrCa 4 Cr 3+ 8 (CO 3 ) 8 SO 4 (OH) 16 · 25H 2 O, a new mineral from Western Australia: description and crystal structure . In: Mineralogical Magazine . tape 78 , 2014, p. 131–144 , doi : 10.1180 / minmag.2014.078.1.10 .
- ↑ a b 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 .
- ↑ a b Putnisite. In: mindat.org. Hudson Institute of Mineralogy, accessed September 5, 2019 .
- ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed September 5, 2019 .