Spodumene
The lithium mineral spodumene is a rarely occurring chain silicate from the group of pyroxenes. It crystallizes in the monoclinic crystal system with the chemical composition LiAl [ Si2O6 ] and usually develops short, flattened crystals, which are clearly striated lengthwise. The size of the crystals often varies from a few centimeters to tens of centimeters, but can also reach record sizes of several meters in some localities.
Special Features
Reiner spodumene is colorless. It can also be caused by foreign admixtures also greenish ( Hiddenite ), white, gray and yellow ( Triphan ) or pink to violet ( Kunzite ) color and two colors. Its pleochroism is strong, that is when viewing the stone along the x- axis it shows a violet to green color and along the z axis, it is colorless.
Occasionally shows spodumene yellow, orange or pink fluorescence under short-and long-wave ultraviolet radiation.
Etymology and history
Was first found spodumene 1800 at Uto in the Swedish countryside Södermanland and described by José Bonifácio de Andrade e Silva, who named " ash -colored " the mineral due to its combustion residues on heating after an ancient Greek word, namely σποδούμενος [ spodúmenos ], which as a present participle passive " burning to ashes; ash -colored "means. The emphasis on the word spodumene is therefore on the middle syllable.
Classification
In the old ( 8th edition ) and new classification of minerals ( 9th Edition ) by Strunz heard of spodumene to the Department of chain and chain silicates ( inosilicates ). The old system shares this department to no further, and summarizes only the members of the pyroxene group together, with the spodumene is allocated to the clinopyroxenes. The new system, however, divided the chains and chain silicates further and the spodumene of the new department of " chains and chain silicates with 2- periodic single chains Si2O6; Pyroxene family " to.
The commonly used in English-speaking classification of minerals according to Dana assigns the spodumene even in the department of chains and chain silicates, there but due to its crystal structure in the sub-division of the chain silicates with simple, unbranched chains, W = 1 with chains P = 2, where he the group of Li- pyroxenes formed as a single member.
Modifications and varieties
Previously known color varieties are
- Of Hiddenite, produce greenish color as a foreign admixtures in which chromium or iron.
- The pink to purple kunzite, which receives its color by admixtures of manganese. Pleochroism, whereby the color viewed from different directions, from deep pink converts to pale or bright pink.
- Colorless to yellowish Triphan
Education and Locations
Spodumene forms either magmatic, with rather cloudy variants arise, or by hydrothermal processes in the pegmatite cavities which produce crisp, high-quality gemstone variants as a characteristic mineral in lithium-rich pegmatites or granites. In most cases, the mineral is found in paragenesis with quartz, albite, Petalite, eukryptite, lepidolite and beryl.
Worldwide, spodumene been at around 450 localities (as of 2010) are detected, among others, Afghanistan, Argentina, Ethiopia, Australia, Bolivia, Brazil, China, Germany, Finland, France, Ireland, Italy, Japan, Canada, Kazakhstan, Korea, Madagascar, Mexico, Mozambique, Myanmar, Namibia, Nigeria, Norway, Austria, Pakistan, Poland, Portugal, Russia, Sweden, Serbia, Zimbabwe, Somalia, Spain, Sri Lanka, South Africa, Swaziland, the Czech Republic, the United Kingdom, USA.
These here is mainly the " Etta Mine" at Keystone in Pennington County (South Dakota ), where the biggest crystals of up to 14 meters in length and 66 tons in weight were found. From the pegmatites at Mawi in Laghman (Afghanistan) up to 40 centimeters long Kunzite could be recovered. The " Pala Chief Mine" on Chief Mountain in California yielded up to 28 centimeters long, Malachite, and from the mines at Resplendor in Minas Gerais (Brazil ) came up to 25 centimeters long Hiddenite.
Crystal structure
Spodumene crystallizes in the monoclinic space group C2 / c with lattice parameters a = 9.474 Å; b = 8.390 Å; c = 5.219 Å and 110.07 ° β =, and four formula units per unit cell.
Detailed structural description see pyroxene.
Use
Spodumene is one of the most important Lithiumerze. In the glass and ceramic industry, it is used as an additive to raw products for the manufacture of, for example, glass-ceramic cooktops, fiber glass or sanitary ware.
As a gemstone
Known Gem varieties are especially Kunzite and Hiddenite that either faceted or sanded to Cabochonen. Kunzite can certainly imitate a pink sapphire or topaz, the Edelberyll morganite, but also the quartz varieties amethyst and rose quartz, depending on the nature of color. When Hiddenite likelihood of confusion exists among other golden beryl ( Heliodor ), the green Demantoid Garnet, the rather light green diopside and rarely, the emerald, and even with chrysoberyl, there were also spodumens with cat's eye effect found.
However, both varieties are due to their good cleavage very sensitive to pressure and heat stress as they arise while grasping and soldering jewelry. When grinding in addition care must be taken due to pleochroistischer effects that the major axis of the crystal is perpendicular to the main panel of the desired facets pulp refiner so that the penetrating light generates strong colors.
Heating to about 300 to 400 ° C, or for prolonged exposure to light, especially by spot irradiation of the stones can fade. Another danger is their sensitivity to hydrofluoric acid, which etches quickly the crystal surfaces and can be dull.