Bavenite
| Bavenite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ca 4 Be 2 Al 2 Si 9 O 26 (OH) 2 |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.DF.25 ( 8th edition : VIII / G.07) 70.05.03.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-pyramidal; mm 2 |
| Space group | On 2 a (No. 40, position 6) |
| Lattice parameters | a = 19.39 Å ; b = 23.19 Å; c = 5.005 Å |
| Formula units | Z = 4 |
| Twinning | To {100} |
| Physical Properties | |
| Mohs hardness | 5.5 to 6 |
| Density (g / cm 3 ) | calculated: 2.69-2.79; measured: 2.71-2.74 |
| Cleavage | Perfect on {001}, good on {100} |
| Break ; Tenacity | uneven |
| colour | Colorless to white; White, green, pink, brown |
| Line color | White |
| transparency | Transparent to translucent |
| shine | Glass to silk gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.578-1.586 n β = 1.579-1.585 n γ = 1.583-1.593 |
| Optical character | Biaxially positive |
| Axis angle | 2V = 22 ° to 58 ° (measured) |
| Other properties | |
| Chemical behavior | soluble in hydrofluoric acid and hydrochloric acid |
Bavenite is a moderately common mineral from the mineral class of silicates and germanates . It crystallizes in the orthorhombic crystal system with the chemical composition Ca 4 Be 2 Al 2 Si 9 O 26 (OH) 2 . It therefore consists of calcium , beryllium , aluminum , silicon as a silicate anion (SiO 4 4− ), oxygen and hydrogen , which is bound in hydroxide ions (OH - ).
With a Mohs hardness of 5.5 to 6, it is one of the minerals that can still be scratched with a steel file. It has a glassy to silky sheen and is transparent to translucent. It is available in different colors; white, green, pink, brown and colorless were reported.
The crystals of bavenite are arranged in rotating groups. They grow up to 6 cm. It forms thin crystals or rosettes , sometimes also needle-like, fibrous or chalky-massive.
Etymology and history
Bavenite was first described by Artini in 1901. However, he overlooked the presence of beryllium in the mineral. Artini named the mineral after the type locality Baveno in Italy . In 1932, Schaller and Fairchild described Bavenit from the "Himalaya mine" in Mesa Grande, California , USA . Fairchild's analysis then showed a beryllium oxide content of 2.67%. Schaller also determines the beryllium content in the Baveno type material. The beryllium content was confirmed again in 1941. In 1946 and 1948, Kutukova, Rowledge and Hayton published analyzes of a mineral containing 6.60 to 7.14% BeO. Rowledge and Hayton called the mineral duplexite . They pointed out the high similarity of the optical values and, due to the higher beryllium content, thought their findings were a new mineral. In a later work, Fleischer and Switzer pointed out that the aluminum and beryllium proportions offset each other. They suspected that duplexite and bavenite were the same mineral after all. This assumption has since been confirmed.
There are two types of Bavenit materials. One is kept at the Museo Civico di Storia Naturale di Milano in Milan , the other in the Muséum national d'histoire naturelle (national museum of natural history) in Paris .
classification
In the outdated, but still in use, 8th edition of the minerals according to Strunz , bavenite is classified in the mineral class of "silicates and germanates". This is further subdivided according to the crystal structure, so that the mineral can be found according to its structure in the group "transition structures between chain and layered silicates ". There he can be found with amstallite , chiavennite , prehnite , rudenkoite and tvedalite in the prehnite-bavenite group , of which he is named. The group has the system number VIII / G.07.
In the 2001 published and comprehensively revised 9th edition of the minerals according to Strunz , which is also used by the International Mineralogical Association (IMA), Bavenit is also classified in the mineral class of silicates and germanates. As in the 8th edition, this is further subdivided according to the crystal structure, so that the mineral is classified according to its structure in the group of "chain and band silicates". However, this is now further subdivided according to the period of the chain, so it can be found here in the group "Chain and band silicates with 2-periodic multiple chains". There it alone forms the unnamed subgroup VIII.DF.25.
In the systematics of minerals according to Dana , which is mainly used in English-speaking countries, bavenite is also in the class of silicates and germanates. There it can be found in the group of "chain silicates: column or tube structures" (No. 70). This group is further subdivided, the mineral can be found here in the subgroup "Chain silicates: column or tube structures with chains connected by Be". There it is the only one in the unnamed group with the system number 70.05.03. The mineral here has the system number 70.05.03.01 .
Crystal structure
Bavenite crystallizes orthorhombically in the space group Am 2 a (space group no. 40, position 6) with the lattice parameters a = 19.39 Å , b = 23.19 Å and c = 5.005 Å and four formula units per unit cell .
properties
morphology
Bavenite forms crystal twins at {100}.
Chemical properties
Bavenit is readily soluble in hydrofluoric acid (HF) and slightly in concentrated hydrochloric acid . In front of the soldering tube , it melts into transparent glass with foam formation .
Physical Properties
Bavenit is weakly piezoelectric .
Education and Locations
Bavenite forms as a druse in granite and pegmatite , formed by the alternation of beryl and other beryllium-containing minerals.
In Germany there are 12 occurrences and other small sites. In Baden-Württemberg there is a deposit in Hohe Waid near Schriesheim . In Bavaria there are 6 deposits, these are in Röhrnbach (Steinerleinbach quarry), in Sauenstein near Schönberg , in Hötzendorf and Matzersdorf (two sites), both near Tittling and in Roßbach near Wald . In Hesse there is a site near the mountain " Das Buch " (near Lindenfels ). There are three deposits in Saxony : one in Beierfeld , one in Schönberg zu Cunewalde and one in Oelsnitz . The last occurrence in Germany is in Thuringia in Weitisberga .
There are even 16 occurrences in Austria . They are located in Carinthia , Lower Austria , Province of Salzburg , Styria , Tyrol and Upper Austria . There are also smaller sites.
In Switzerland there are smaller sites, but only one occurrence: It is located on Lai Blau (a mountain) near Tujetsch in the canton of Graubünden .
In total, Bavenit can be found at 239 (as of 2015) locations. These are in Afghanistan , Australia , Bulgaria , China , Germany, Finland , France , Greenland , Italy, Japan , Canada , Madagascar , Mongolia , Namibia , Austria, Pakistan , Poland , Portugal , Russia , Spain , Sweden , Switzerland, South Africa , Czech Republic , the United Kingdom and the US states of California, Connecticut , Maine , New Hampshire , North Carolina , Virginia and Wisconsin .
See also
literature
- E. Ardini: Di una nuova specie minerale trovata nel granito di Baveno In: Atti della Reale Accademia dei Lincei , Vol. 10, 1901, pp. 139–145 ( PDF , Italian)
- George Switzer, Laura E. Reichen: Re-examination of pilinite and its identification with bavenite In: American Mineralogist , Vol. 45, 1960, pp. 757–762 ( PDF )
- LG Berry: The composition of bavenite In: American Mineralogist , Vol. 48, 1963, pp. 1166–1168 ( PDF )
- E. Cannilo, A. Coda, G. Fagini: The crystal structure of bavenite In: Acta crystallographica , Vol. 20, 1966, 301-309, doi : 10.1107 / S0365110X66000586
Web links
- American-Mineralogist-Crystal-Structure-Database - Bavenite
- Database-of-Raman-spectroscopy - Bavenite
Individual evidence
- ↑ a b c d e f g Bavenite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 59, 7 kB )
- ↑ a b c d Webmineral - Bavenite
- ↑ a b Mineralienatlas: Bavenit
- ↑ Michael Fleischer, George Switzer: The bavenite problem In: American Mineralogist , Vol. 38, November / December 1953, pp. 988–993 ( PDF , English)
- ^ LG Berry: The composition of bavenite In: American Mineralogist , Vol. 48, 1963, pp. 1166–1168 ( PDF )
- ↑ a b c Mindat - Bavenite