Henmilit
| Henmilit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1981-050 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Borates ( monoborates ) |
|
System no. to Strunz and to Dana |
6.AC.30 ( 8th edition : V / G.09) 01/26/05/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 5.7617 Å ; b = 7.9774 Å; c = 5.6488 Å, α = 109.611 °; β = 91.473 °; γ = 83.686 ° |
| Formula units | Z = 1 |
| Frequent crystal faces | {100}, {010}, {101}, {102}, {110}, {0 1 1}, { 1 4 2} |
| Physical Properties | |
| Mohs hardness | <2.5, Vickers hardness VHN 25 = 193-206 kg / mm 2 |
| Density (g / cm 3 ) | 2.51 (measured); 2.523 (calculated) |
| Cleavage | very perfect after {001}, good after {110} |
| Break ; Tenacity | not specified; brittle |
| colour | bluish purple |
| Line color | very pale purple to almost white |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.585 n β = 1.608 (calculated) n γ = 1.615 |
| Birefringence | δ = 0.030 |
| Optical character | biaxial negative |
| Axis angle | 2V = 58 ° |
| Pleochroism | strong from X = pale pink through Y = pale violet to Z = very pale blue |
| Other properties | |
| Chemical behavior | Easily soluble in 1: 2 diluted HCl and 1: 2 diluted HNO 3 |
| Special features | disintegrates under the electron beam |
Henmilite is a very rare mineral from the mineral class of " borates " (formerly carbonates, nitrates and borates, see classification ). It crystallizes in the triclinic crystal system with the chemical formula Ca 2 Cu 2+ [(OH) 2 | B (OH) 4 ] 2 , and is thus chemically seen a calcium - copper - borate with additional hydroxide that is structurally to the Mono borates belongs.
Henmilite forms prismatic-pinacoidal crystals up to 3 mm in size , which show characteristic bluish -violet hues. There are also massive, coarse aggregates . The mineral is found exclusively in the Fuka mine, located 40 km northeast of Okayama in the city Takahashi in Okayama Prefecture within the region Chūgoku on Honshu in Japan is. Henmilit occurs here in cavities in boron-mineralized dikes within contact metasomatically transformed limestones and is u. a. accompanied by pentahydroborite and olshanskyite .
Etymology and history
During the investigation of boron mineral-bearing veins in the Fuka mine, a mineral closely associated with pentahydroborite, which is very conspicuous due to its blue-violet color, was discovered. In detailed investigations, this phase turned out to be the first example of a borate with both calcium and copper and thus a new mineral.
The mineral was recognized by the International Mineralogical Association (IMA) in 1981 and first described as a henmilite in 1986 by a team of Japanese scientists led by Izumi Nakai from the University of Tsukuba and Hisashi Okada , Kazunosuke Masutomi , Eiji Koyama and Kozo Nagashima . It was named after Professor Kitinosuke Henmi (1919–1997) and his daughter Chiyoko Henmi (* 1949) from the Department of Earth Science at Okayama University in Okayama in recognition of their mineralogical work in the Fuka skarn deposit, which led to the identification of three new minerals ( Bicchulit , Fukalit and Oyelit ).
Type material of the mineral is stored in the National Museum of Natural Sciences , Shinjuku near Tokyo , (Catalog No. M-24641) and in the National Museum of Natural History , Washington, DC , USA , (Catalog No. 165482).
classification
In the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , the Henmilit belonged to the common mineral class of "carbonates, nitrates and borates" and there to the department of "island borates", where together with Frolovit it created the unnamed group with the system No. V / G.09 formed.
The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), assigns the Henmilit to the newly defined class of "borates" and there into the department of "monoborates". This is further subdivided according to the structure of the borate complex and the possible presence of additional anions , so that the mineral is classified according to its composition in the subsection “B (O, OH) 4 , with and without additional anions; 1 (T), 1 (T) + OH etc. ”is to be found, where it is the only member of the unnamed group 6.AC.30 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking area , assigns the Henmilit, like the outdated Strunz system, to the common class of "carbonates, nitrates and borates" and there to the department and subdivision of the same name of "hydrous borates with hydroxyl or halogen" a. Here you can find him as the only member of the unnamed group 01/26/05 .
Chemism
Henmilit has (based on 12 oxygen atoms per formula) the measured composition Ca 1.91 Cu 0.99 B 2.05 O 12 H 12.03 , which was idealized to Ca 2 CuB 2 (OH) 12 and contents of 18, Requires 85 B 2 O 3 , 21.53% CuO, 30.36% CaO, and 28.26% H 2 O.
Crystal structure
Henmilite crystallizes in the triclinic crystal system in the space group P 1 (space group no. 2) with the lattice parameters a = 5.7617 Å ; b = 7.9774 Å; c = 5.6488 Å; α = 109.611 °; β = 91.473 ° and γ = 83.686 ° and one formula unit per unit cell .
In henmilite, boron is found in isolated B (OH) 4 groups and copper has a square-planar coordination through hydroxide ions. Calcium is surrounded by eight hydroxide ions. The structure of the Henmilits consists of dimers of edge-sharing Ca (OH) 2 - polyhedra by the square planar Cu (OH) 4 groups are joined to form a layer structure parallel [01 1 is produced]. The layers are B (OH) 4 - tetrahedra linked to form a three-dimensional scaffold. The Henmilit structure can also be described in such a way that dimers of Ca polyhedra are linked by two B (OH) 4 tetrahedra in such a way that chains are formed in parallel [001]. These chains are linked by square-planar Cu (OH) 4 groups to form a three-dimensional framework.
properties
morphology
Henmilite forms crystalline masses embedded in marbles as well as - in cavities in pentaborite corridors - also up to 3 mm large, sharp-edged and shaped crystals that sit on the surface of the pentaborite or are fused with it. The main crystal form of the idiomorphic, pinacoidal crystals, which determines the costume, is the well-developed first pinacoid {100}. In the case of crystals with less area, the second pinacoid {010}, the pinacoid parallel to the b-axis {101} and {10 1 } and the pinacoid parallel to the c-axis {110} and {1 1 0} are added. The pinacoids {102}, {0 1 1} and {14 2 } can also be identified on larger-area crystals (see also the crystal drawings on the right).
physical and chemical properties
The color of the Henmilit crystals is a characteristic bluish violet in all cases. The line color of the henmilit, on the other hand, varies from very pale purple to almost white. The surfaces of the transparent crystals have a strong glass-like sheen . In the thin section the mineral shows a strong pleochroism under the microscope from X = pale pink to Y = pale violet to Z = very pale blue.
Henmilit has a very perfect cleavage according to {001} and good cleavage according to {110}, but breaks very easily due to its brittleness ("fragile"), although no information is available on the type of fracture surface. With a Mohs hardness of <2.5 and a Vickers hardness of VHN 25 = 193–206 kg / mm 2 , the Henmilit described as “soft” is one of the soft minerals that, like the reference mineral plaster of paris, can at least be scratched with a fingernail. The measured density for Henmilit is 2.51 g / cm³, the calculated density for the mineral is 2.523 g / cm³.
Henmilit is easily soluble in 1: 2 diluted hydrochloric acid and 1: 2 diluted nitric acid.
Education and Locations
As a very rare mineral formation, Henmilit could so far (as of 2016) only be described by its type locality . This is the former marble - quarry of Fuka mine, 40 km northeast of Okayama in the city Takahashi in Okayama Prefecture within the region Chūgoku on Honshu in Japan is.
Today the mine works underground. A high-purity calcite is mined, which u. a. is used for toothpaste . The Fuka mine is world famous for appearing here as Skarnminerale Bicchulit, Fukalit, Oyelit, spurrite , gehlenite and Rank Init . They come from a boron-containing high-temperature calcium silicate yarn with an extremely low iron content, which developed at the boundary between a limestone body and a Monzonitic intrusive rock . The minerals mentioned are almost without exception hydrogenated calcium silicates, which were formed by high-temperature metamorphosis and metasomatosis of the limestone and subsequent hydration reactions.
Henmilite is found in the Fuka mine in cavities in boron-mineralized veins within contact metasomatically transformed limestones and is accompanied by pentahydroborite, olshanskyite, tenorite , sillenite , bultfonteinite , cuspidin , thaumasite , brucite and calcite .
use
Despite the high boron and copper content, henmilite is of no importance as either boron or copper ore due to its rarity. In contrast, there is a strong demand for the attractive blue crystals in mineral collectors' circles.
See also
literature
- Izumi Nakai, Hisashi Okada, Kazunosuke Masutomi, Eiji Koyama, Kozo Nagashima: Henmilite, Ca 2 Cu (OH) 4 [B (OH) 4 ] 2 , a new mineral from Fuka, Okayama Prefecture, Japan. Part I. Occurrence and description . In: The American Mineralogist . tape 71 , 1986, pp. 1234-1236 .
- Henmilite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF, 65.8 kB )
Web links
- Mineral Atlas: Henmilit (Wiki)
- Webmineral - Henmilite
- Mindat - Henmilit
- RRUFF Database-of-Raman-spectroscopy - Henmilit
- American-Mineralogist-Crystal-Structure-Database - Henmilit
Individual evidence
- ^ A b 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. 336 .
- ↑ a b c d e f g h i j k l m n o Izumi Nakai, Hisashi Okada, Kazunosuke Masutomi, Eiji Koyama, Kozo Nagashima: Henmilite, Ca 2 Cu (OH) 4 [B (OH) 4 ] 2 , a new mineral from Fuka, Okayama Prefecture, Japan. Part I. Occurrence and description . In: The American Mineralogist . tape 71 , 1986, pp. 1234–1236 ( rruff.info [PDF; 700 kB ]).
- ↑ a b c d Henmilit. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( PDF, 65.8 kB )
- ↑ a b c Isao Kusachi: New data on mineralogical properties of henmilite (in Japanese with English abs.) . In: Journal of the Mineralogical Society of Japan . tape 21 , 1992, p. 127–130 ( jstage.jst.go.jp [PDF; 423 kB ]).
- ↑ a b Izumi Nakai: Henmilite, Ca 2 Cu (OH) 4 [B (OH) 4 ] 2 , a new mineral from Fuka, Okayama Prefecture, Japan. Part II. Crystal structure . In: The American Mineralogist . tape 71 , 1986, pp. 1236–1239 ( rruff.info [PDF; 700 kB ]).
- ↑ Mindat - Number of localities for Henmilit
- ↑ Find location list for carletonite in the Mineralienatlas and Mindat
- ↑ Mindat - type locality for Henmilit