Junitoite

Junitoite
Junitoite crystals with a glossy finish that resemble mother-of-pearl (size approx. 4 mm)
General and classification
other names	IMA 1975-042
chemical formula	CaZn 2 [4] [Si 2 O 7 ] · H 2 O
Mineral class (and possibly department)	Silicates and Germanates
System no. to Strunz and to Dana	9.BD.15 ( 8th edition : VIII / C.07) 56.02.01.01
Crystallographic Data
Crystal system	orthorhombic
Crystal class ; symbol	orthorhombic-pyramidal; mm 2
Space group	Ama 2 (No. 40)
Lattice parameters	a  = 12.51  Å ; b  = 6.32 Å; c  = 8.56 Å
Formula units	Z  = 4
Physical Properties
Mohs hardness	4.5
Density (g / cm 3 )	measured: 3.5 (1); calculated: 3.516
Cleavage	good after {100}; indistinct after {010} and {011}
Break ; Tenacity	brittle
colour	colorless, white, also slightly different colors due to weathering
Line color	White
transparency	transparent to translucent
shine	Glass gloss
Crystal optics
Refractive indices	n α  = 1.656 n β  = 1.664 n γ  = 1.672
Birefringence	δ = 0.016
Optical character	biaxial positive
Axis angle	2V = measured: 86 °; calculated: 88 °
Other properties
Special features	strongly pyroelectric

Junitoite is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition CaZn ₂ ^[4] [Si ₂ O ₇ ] · H ₂ O and has so far only been found in the form of hemimorphic ( half- shaped ) crystals up to about 5 mm in size.

Etymology and history

Junitoite was first found in 1976 in the "Christmas Mine" near the town of Christmas in the Banner district of the US state of Arizona .

The mineral was scientifically described by SA Williams, who named it after Dr. Jun Ito (1926–1978), a Japanese-American mineral chemist from Harvard University .

classification

In the meanwhile outdated but still in use systematics of minerals according to Strunz (8th edition) , Junitoite still belongs to the general division of " Group silicates (sorosilicates)", where it forms a separate group with bertrandite and hemimorphite .

Since the revision of Strunz's mineral classification in the 9th edition , this section has been subdivided more precisely according to the type of silicate complexes occurring in the compound and the coordination of the cations involved . The Junitoite can be found accordingly in the subsection of "Group silicates with Si ₂ O ₇ groups with additional anions and cations in tetrahedral [4] and / or other coordination", where it is the only member of the unnamed group 9.BD.15 .

The systematics used in the English-speaking world of minerals according to Dana also assigns Junitoite to the group of silicates, but there in the subdivision of " Group silicates: Si ₂ O ₇ groups and O, OH, F and H ₂ O with cations in [ 4] and / or> [4] coordination ”. There he is the only member of the unnamed group 56.2.1 .

Crystal structure

Junitoite crystallizes orthorhombically in the space group Ama 2 (space group no. 40) with the lattice parameters a  = 12.51  Å ; b  = 6.32 Å and c  = 8.56 Å and 4 formula units per unit cell .

Education and Locations

Junitoite forms in regressively formed tactite zones, i.e. in rock zones with a complex structure created by contact metamorphosis . There it occurs in paragenesis with apophyllite , calcite , kinoite , smectite and xonotlite, among others .

So far, apart from its type locality “Christmas Mine” (Banner, Arizona) , Junitoite could only be detected in the “Franklin Mine” near Franklin in Sussex County (New Jersey), which is also located in the USA .

See also

• List of minerals

literature

• Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 691 (first edition: 1891).

Web links

Commons : Junitoite  - collection of images, videos and audio files

• Mineral Atlas: Junitoite (Wiki)
• Webmineral - Junitoite (English)

Individual evidence

1. ↑ ^{a b c d e} Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  573 .
2. ↑ Webmineral - Junitoite (English)
3. ↑ ^{a b c d e} Junitoite . 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; 70  kB ]).
4. ↑ ^{a b c d e} Mindat - Junitoite (English)
5. ↑ Find location list for Junitoite at the Mineralienatlas and at Mindat