Nahcolith
| Nahcolith | |
|---|---|
 |
|
| General and classification | |
| other names |
Thermokalit |
| chemical formula | NaHCO 3 |
|
Mineral class (and possibly department) |
Carbonates and nitrates (formerly carbonates, nitrates and borates) |
|
System no. to Strunz and to Dana |
5.AA.15 ( 8th edition : V / B.01) 01/13/01/01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 3.51 Å ; b = 9.71 Å; c = 8.05 Å β = 111.8 ° |
| Formula units | Z = 4 |
| Frequent crystal faces | {010}, {110}, {101}, {120}, { 1 01}, {111} |
| Twinning | Contact and Penetration Twins, Twin Level (101) |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | measured: 2.21 to 2.238; calculated: 2.16 |
| Cleavage | completely after {101}, good after {111}, clearly after {100} |
| Break ; Tenacity | shell-like |
| colour | colorless, white, gray, yellow, reddish brown to black |
| Line color | White |
| transparency | transparent |
| shine | Glass sheen, greasy sheen on cleavage surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.377 n β = 1.503 n γ = 1.583 |
| Birefringence | δ = 0.206 |
| Optical character | biaxial negative |
| Other properties | |
| Chemical behavior | water soluble |
Nahcolith is a rarely occurring mineral from the mineral class of " carbonates and nitrates " (formerly carbonates, nitrates and borates). It crystallizes in the monoclinic crystal system with the composition NaHCO 3 , so from a chemical point of view it is sodium hydrogen carbonate .
Nahcolith rarely develops prismatic crystals . It usually occurs in the form of porous mineral aggregates and efflorescence. In its pure form it is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a gray, yellowish or reddish-brown to black color, the transparency decreasing accordingly to the point of opacity.
With a Mohs hardness of 2.5, Nahcolith is one of the soft minerals and, like the reference minerals gypsum or halite (2) and calcite (3), can either be scratched with a fingernail or with a copper coin. The surfaces of undamaged crystals have a more glass-like gloss , whereas the cleavage surfaces have a greasy sheen .
Special properties
Nahcolit is easily soluble in water and should therefore be stored away from moisture.
Etymology and history
Nahcolith was first discovered on Vesuvius , more precisely in the "Atrio del Cavallo" (western part of the "Valle del Gigante") in Italy and described in 1928 by Frederick Allen Bannister (1901–1970), who named the mineral according to its chemical composition (NaHCO 3 , Sodium hydrogen carbonate ) and the Greek word for “stone” λίθος lithos .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Nahcolith belonged to the mineral class of "carbonates, nitrates and borates" and there to the division of "anhydrous carbonates [CO 3 ] 2− without foreign anions ", where it belonged together with Kalicinit the "Nahcolith Kalicinit Group" with the system no. V / B.01 and the other members Natrit , Teschemacherit , Wegscheiderit and Zabuyelit .
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 the Nahcolith to the reduced class of “carbonates and nitrates”, but there also to the “carbonates without additional anions” section; without H 2 O “. However, this is further subdivided according to the affiliation of the cations involved to certain element groups , so that the mineral can be found in the sub-section “ Alkali Carbonate” according to its composition , where it is the only member of the unnamed group 5.AA.15 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Nahcolith, like the outdated Strunzian systematics, to the common class of "carbonates, nitrates and borates" and there in the department of "carbonates". Here he is to be found as the only member of the unnamed group 01/13/01 within the sub-section “ Acid carbonates with various formulas ”.
Education and Locations
Nahcolith forms as precipitation near hot springs or as efflorescence during evaporation processes around salt lakes and lyes. It can also be found secondary in the form of transformation margins on Thermonatrite . As Begleitminerale occur next thermonatrite among other things, further evaporite -mineral as borax , Burkeite , Gaylussite , halite , Northupit , Thenardite and Trona .
As a rare mineral formation, Nahcolith could only be detected at a few sites, whereby so far (as of 2013) around 50 sites are known. In addition to its type locality "Atrio del Cavallo" on Vesuvius , the mineral could also be found in Italy on the Solfatara near Pozzuoli in the Phlegraean Fields .
Well-known European sites include the “La Wiltz brook” quarry near Bastogne in Belgium , the slag heaps of the Ochsenhütte near Goslar (Lower Saxony), the Genna zinc works near Letmathe (North Rhine-Westphalia) and the “Gottesbelohnung” copper and silver works near Hettstedt (Saxony -Anhalt) in Germany , the Sokli carbonatite complex near the municipality of Savukoski in Finland , the thermal springs near Abrest in France and around Karlsbad in the Czech Republic , Ditrău in the Harghita district in Romania , Kukiswumtschorr in the Chibinen and Alluaiw in the Lowosero massif in the Lowosero-Tundra , both on the Russian Kola Peninsula , as well as Alnön and Sandfors ( Västerbotten ) in Sweden and the salt pits near Bex in Switzerland .
Other locations are in Egypt, Chile, China, Finland, Greenland, Canada, Kenya, Mexico, Mozambique, Namibia, Tajikistan, Tanzania and in several states of the USA.
Crystal structure
Nahcolith crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a = 3.51 Å ; b = 9.71 Å; c = 8.05 Å and β = 111.8 ° and 4 formula units per unit cell .
See also
literature
- FA Bannister: The so-called 'thermokalite' and the existence of sodium bicarbonate as a mineral. In: Mineralogical Magazine. Volume 22, 1929, pp. 53-64. ( PDF 564.6 kB )
- Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin / New York 1981, ISBN 3-11-006823-0 , p. 502 .
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 564 (first edition: 1891).
Web links
Individual evidence
- ↑ a b c d e 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. 285 .
- ↑ a b c Nahcolite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF 65.5 kB )
- ↑ a b Mindat - Nahcolite
- ↑ Mindat - Number of localities for Nahcolith
- ↑ a b List of localities for Nahcolith in the Mineralienatlas and Mindat