Eucryptite
- Deep - eukryptite
- Lithionnephelin
Eukryptite is a rarely occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the trigonal crystal system, with the chemical composition LiAl [ SiO4 ], that is, a lithium-aluminum silicate, which belongs structurally to the island silicates ( Nesosilikaten ).
Eukryptite usually comes in the form fibrillar or coarse -grained to massive mineral aggregates before, but is rarely euhedral crystals of up to three inches in size, their surfaces have a glass-like shine. In its pure form eukryptite is colorless and transparent. But it may also appear white and accept by foreign admixtures a pink or brownish color by multiple refraction due to the usually polycrystalline training, the transparency decreases accordingly.
Special Features
Under short-wave UV light indicate some Eukryptite a pink to red or orange fluorescence, similar to that of neon highlighters.
Eucryptite in the modification of β -eucryptite has a negative thermal expansion coefficient, a high chemical and thermal stability and a good lithium ionic conductivity.
Etymology and history
Was first discovered Euktyptit in the quarry " Fillow " in Branchville in Fairfield County of the U.S. state of Connecticut and described in 1880 by George J. Brush and Edward S. Dana, which is the mineral by the Ancient Greek words εὐ [ eu] for " good" or " beautiful "and κρυπτός [ kryptós ] for" hidden "or" secret named ". The name refers to the fact that eukryptite occurs most intimately connected with albite and is therefore difficult to analyze.
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of eukryptite to the Department of " island silicates ( nesosilicates ) " where he. Together with Phenakit and Willemite the " Phenakit series" with the System No. VIII/A.01 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the eukryptite also in the department of " island silicates ( nesosilicates ) ". However, this is further subdivided according to the possible presence of additional anions and the coordination of the cations involved, so that the mineral according to its composition in the subsection " island silicates without other anions; Cations "can be found, where it also together with Phenakit, willemite, and further with the Xingsaoit " in tetrahedral coordination Phenakitgruppe "with the system no. 9.AA.05 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the eukryptite in the department of " island silicate minerals ", where he. Together with Phenakit and willemite in the " Phenakitgruppe " with the System No. Can be found: " SiO4 groups with cations in coordination island silicates " 51.01.01 within the subdivision.
Education and Locations
Eukryptite forms in lithium-rich granitic pegmatites, where it is usually found in weathered spodumene. However, it can also arise primarily and form up to 30 centimeters large masses. Other accompanying minerals include albite, Amblygonite, Lepidolite, Petalite and quartz.
A rare mineral formation eukryptite could be detected only in a few localities, where so far (as of 2013) are about 30 localities known as. Apart from its type locality, the quarry " Fillow " at Branchville mineral occurred in the United States still at White Picacho and the "Independence Mine" in Yavapai County Arizona, at Collins Hill near Portland, Middlesex County, Connecticut, at the Parker Mountain in Strafford County of New Hampshire, on the " Harding Mine" at Picuris Pueblo in Taos County New Mexico, at Hiddenite and Kings Mountain in Alexander County North Carolina as well as in the " Etta Mine" at Keystone in Pennington County South Dakota.
Other localities lie among other things in Egypt, Australia, China, Finland, Canada, Namibia, Portugal, Russia, Sweden, Zimbabwe, Spain and South Africa.
Crystal structure
Eukryptite trigonal crystallized in the space group R3 ( Raumgruppen-Nr. 148) with the lattice parameters a = 13.47 Å and c = 9.00 Å and 18 formula units per unit cell.
Use
Eukryptite is an important raw material for the production of glass ceramics and superionic conductor due to special physical properties.