Creedite
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Creedit is a rarely occurring mineral from the mineral class of " halides ". It crystallizes in the monoclinic crystal system with the chemical composition Ca 3 [ Al 2 ( F, OH ) 10 | SO4 ] · 2H2O, with that given in the parentheses fluorine or hydroxide ion is in the formula each represent each other (substitution, Diadochie ) but always in the same proportions are to the other components of the mineral.
Creedit most developed prismatic, acicular or flaky crystals with glass-like sheen on the surfaces, which can be arranged in radialstrahligen, drusy or granular mineral aggregates. In pure form, the mineral is colorless and transparent, but it can appear white due to training or multi-crystalline lattice defects and an orange accept by foreign admixtures to reddish or violet to bluish color by multiple refraction, its transparency decreases accordingly. His stroke color, however, is always white.
Etymology and history
Was first discovered Creedit together with Gearksutite 1915 on the slag heap of Wagon Wheel Gap of Mineral County (Colorado) lying " Colorado Fluorspar Co. Mine". Esper S. Larsen and Roger C. Wells described the mineral in 1916 and named it after the area close to the town of Creede locality.
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of Creedit to the mineral class of " halides " and then to the Department of " Doppelhalogenide, hydrated ," where he, along with Acuminit, Artroeit, Chukhrovit - (Ce) Chukhrovit - (Y), and Gearksutite Tikhonenkovit was the unnamed group III/C.01.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Creedit also in the class of " halides ", there, however, in the department of " complexes halides " one. This department is also further subdivided by the structural configuration so that the mineral can be found in the corresponding sub-division of " Aluminofluoride with CO3, SO4, PO4 ", where it forms the unnamed group 3.CG.15 the only member.
The mainly common in English-speaking classification of minerals according to Dana assigns the Creedit in the class of " halides " and then in the Department of the ( general ) " halide " one. Here he can be found as the only member of the unnamed group 12:01:04 within the subdivision " halide compounds with different anions ."
Education and Locations
Creedit forms in fluoritreichen hydrothermal deposits. The type material was found in the form of white to colorless grains and less developed crystals to about 5 millimeters size, embedded in matt - white kaolinite and little barite. It was later in the deposit of the Wagon Wheel Gap also reddish, several centimeters large crystals.
A rare mineral formation Creedit previously could (as of 2012) are detected only at a few localities, of which approximately 50 localities are known. Apart from its type locality Colorado Fluorspar Co. mine the mineral nor entered the United States in the also in Colorado lying " Henderson Mine" ( Clear Creek County) and in the " open pit Cresson " ( Teller County ), and at several locations in the states of Arizona, California, Nevada and New Mexico on.
Known due to exceptional Creeditfunde are among other Santa Eulalia in the municipality of Aquiles Serdán in the Mexican state of Chihuahua, where rich drusen were found. Very well developed and up to three inches long crystals were also in the " Aqschatau Mine" in Kazakhstan revealed.
Other localities lie among others in Bolivia, China, France, Greece, Italy, South Africa and Tajikistan.
Crystal structure
Creedit crystallizes in the monoclinic space group C2 / c ( Raumgruppen-Nr. 15) with the lattice parameters a = 13.94 Å; b = 8.61 Å; c = 9.99 Å and 94.4 ° β = 4 and formula units per unit cell.