Matlockite
| Matlockite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | PbFCl |
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.DC.25 ( 8th edition : III / D.09) 02/09/11/01 |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | ditetragonal-dipyramidal; 4 / m 2 / m 2 / m |
| Space group | P 4 / nmm (No. 129) |
| Lattice parameters | a = 4.110 Å ; c = 7.246 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | (001), (110), subordinate (100), (101), (111) |
| Physical Properties | |
| Mohs hardness | 2.5 to 3 |
| Density (g / cm 3 ) | measured: 7.21; calculated: 7.16 |
| Cleavage | completely after (001) |
| Break ; Tenacity | uneven to slightly scalloped |
| colour | colorless, light yellow to amber yellow, yellow-orange, greenish |
| Line color | White |
| transparency | transparent to translucent |
| shine | Diamond luster, pearlescent luster according to {001} |
| Crystal optics | |
| Refractive indices |
n ω = 2.152 n ε = 2.012 (for wavelength 564 nm) |
| Birefringence | δ = 0.140 (564 nm) |
| Optical character | uniaxial negative |
| Other properties | |
| Chemical behavior | soluble in nitric acid and conc. HCl |
Matlockite is a rarely occurring mineral from the mineral class of " halides ". It crystallizes in the tetragonal crystal system with the chemical composition PbFCl, i.e. it consists of equal parts of lead , fluorine and chlorine .
Matlockite mostly develops transparent to translucent, tabular crystals with diamond luster on the crystal surfaces and pearlescent luster on the cleavage surfaces. Lamellar, rosette-shaped or radial-radial mineral aggregates are also known. Pure matlockite is colorless and transparent. However, it can also be from light yellow to amber-yellow , yellow- orange or greenish in color due to foreign admixtures. However, the line color is always white.
Etymology and history
Probably the first mention of matlockite comes from John Mawes descriptions of the Mineralogy of Derbyshire in 1802.
The mineral was first described scientifically in 1851 by Robert Philips Greg in samples from a dump in the mine in the parish of Cromford , near the town of Matlock in Derbyshire , England . The chemical analysis overlooked the fluorine levels and consequently Greg described the new mineral as lead oxychloride (Pb 2 O Cl 2 ). He named it after the town of Matlock, which was located near the type locality , as the name cromfordite (now phosgenite ) had already been taken.
It took around 80 years until in 1933 W. Nieuwenkamp, who had previously investigated the structure of synthetic PbFCl, detected fluorine in matlockite and was able to show that matlockite and PbFCl are chemically and structurally identical. Nieuwenkamp's results in 1934 were confirmed by FA Bannister and MH Hey, which determined the structure of natural matlockite and its optical properties.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the matlockite belonged to the mineral class of "halides" and there to the department of "oxyhalides", where together with Bismoclit , Daubréeit , Rorisit and Zavaritskit it belongs to the unnamed group III / D .09 made.
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 matlockite to the "halides" class, but in the "oxyhalides, hydroxyhalides and related double halides" category. a. This section is also further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the subdivision "With Pb (As, Sb, Bi) without Cu", where it is named after the "Matlockite group" the system no. 3.DC.25 and the other members Bismoclit, Daubréeit, Rorisit, Zavaritskit and Zhangpeishanit .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the matlockite to the class of "halides" and there in the department of "halides". Here he is also the namesake of the "Matlockit group" with the system no. 09.02.11 and the other members Rorisit and Zhangpeishanit can be found within the sub-section of " Anhydrous and water-containing halides with the formula AX 2 ".
Crystal structure
Matlockite crystallizes tetragonally in the space group P 4 / nmm (space group no. 129) with the lattice parameters a = 4.11 Å and c = 7.246 Å as well as 2 formula units per unit cell .
The lead atom is surrounded by 9 anions (4 × F −1 and 5 × Cl −1 ) in the form of a simply capped square antiprism. Most of the time, lead is only surrounded by 8 anions. The unusual 9-fold coordination of lead can be found e.g. B. also with phosgenite .
The fluorine ion is tetrahedrally surrounded by 4 lead cations and the chlorine ion is square pyramidal by 5 lead ions.
properties
Matlockite decomposes when heated and melts into gray-yellow spheres on charcoal , giving off acid vapors. It also dissolves easily in nitric acid . It is insoluble in dilute hydrochloric acid , whereas it is soluble in concentrated hydrochloric acid with the formation of chloroplumbates.
Education and Locations
Matlockite forms as a secondary mineral in the oxidation zone of lead-containing deposits of galena ( lead luster , PbS). Accompanying minerals are mostly galena, but also angelsite , barite , bolite , caledonite , cerussite , diabolite , fluorite , leadhillite , phosgenite and sphalerite .
In total, Matlockite has been detected at around 30 sites so far (as of 2011). In addition to its type locality Cromford near Matlock, the mineral occurred in England in the nearby "Bage Mine" near Bolehill in Derbyshire ; at Crantock in Cornwall and in the "Waterbank Mine" at Ecton in Staffordshire .
In Germany, matlockite is so far only known from the Christian Levin colliery near Essen in North Rhine-Westphalia and the only previously known site in Austria is Waitschach in Carinthia.
A very large four- inch crystal from Derbyshire is in the collections of the American Museum of Natural History . The Derby Museum and Art Gallery has a sample that is seven centimeters in size.
Other locations are Tasmania in Australia, Antofagasta and Tarapacá in Chile, Mengyin in China, Marvejols in France, Lavrio in Greece, the Italian province of Livorno , Kadoma in Zimbabwe, Argent in the South African province of Gauteng and Spruce in Elko County in Nevada, Spearfish in Lawrence County in South Dakota and several locations in Arizona in the United States (USA).
See also
literature
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 495 .
Web links
- Mineral Atlas: Matlockite (Wiki)
Individual evidence
- ↑ a b c W. Nieuwenkamp: The chemical composition of matlockite . In: Journal of Crystallography . tape 86 , 1933, pp. 470–471 ( rruff.info [PDF; 105 kB ; accessed on January 8, 2017]).
- ↑ a b c d e f g h i j k l m n FA Bannister, MH Hey: The crystal-structure and optical properties of matlockite (PbFCl) . In: Mineralogical Magazine . tape 23 , 1934, pp. 587–597 ( rruff.info [PDF; 497 kB ; accessed on January 8, 2017]).
- ↑ a b c d e f g M. Pasero, N. Perchiazzi: Crystal structure refinement of matlockite . In: Mineralogical Magazine . tape 60 , 1996, pp. 833–836 ( rruff.info [PDF; 276 kB ; accessed on January 8, 2017]).
- ↑ a b c d e f g h i j RP Greg: A description of matlockite, a new oxychloride of lead . In: The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science . tape 2 , 1851, pp. 120–121 ( rruff.info [PDF; 149 kB ; accessed on January 8, 2017]).
- ^ John Mawe: The Mineralogy of Derbyshire with a Description of the Most Interesting Mines . 1802, London
- ↑ a b Robert Philips Greg, William Garrow Lettsom: Matlockit , in: Manual of the mineralogy of Great Britain & Ireland in the Google book search
- ↑ Gerhart Jander, Ewald Blasius, Joachim Strähle: Introduction to the inorganic-chemical internship . 15th edition. Hirzel, Stuttgart 2005, ISBN 3-7776-1364-9 .
- ↑ Matlockite . 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; 60 kB ; accessed on January 8, 2017]).
- ↑ Clifford Frondel : The size of crystals . In: American Mineralogist . No. 20 , 1935, pp. 469–473 ( minsocam.org [PDF; 300 kB ; accessed on January 8, 2017]).
- ^ N. Moyes: Working with Wikipedia - a museum's perspective time 14:30