Cavansite
- IMA 1967-019
Cavansit is a rarely occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition Ca [ V 4 O | Si4O10 ] · 4H2O, and is therefore a calcium - vanadium - layer silicate.
Cavansit is transparent and develops long, prismatic to acicular crystals, but also radial- mineral aggregates of blue to greenish blue color with vitreous luster on the surfaces.
Etymology and history
The name Cavansit is a portmanteau consisting of the abbreviations contained in the mineral major elements calcium (Ca), vanadium (V, van ) and silicon ( Si) and the attached 't' after the Greek word lithos for stone.
Cavansit was first discovered in the autumn of 1960 by Mr. and Mrs. Leslie Perrigo. These were to a large rock wall near the Owyhee Dam in Oregon a blue mineral and gathered together with Mr. and Mrs. Frank Zimmerman some samples and handed them over to Dr. Paul Desautels from the United States National Museum, who realized that this may have been a could act new mineral.
Three years later, the Amateurmineraloge and collector John Cowles discovered (1907-1985) a similar looking, blue mineral in the quarry " Charles W. Chapman " in Goble about 350 miles northwest of the Owyhee Dam and showed it to Lloyd W. Staples with the request, to identify the mineral. Staples analyzed it together with Howard T. Evans (Jr. ) and James R. Lindsay and realized the one hand, that it was identical to the material of the Owyhee Dam and a previously unknown mineral species. While the crystallographic analysis were at a sample of the Owyhee Dam on some of crystal twins which, although similar to the Cavansit in appearance and physical properties and also had the same chemical composition. However, the crystals differed in the structure of the silicate layers from Cavansit. Staples, Evans and Lindsay also called this new mineral Pentagonit based on its characteristic pentagonal crystal twins.
Since naming the Minerals of Cowles did not materialize due to unfortunate circumstances, the mineral Cowlesit was later named after him for compensation.
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of Cavansit to the mineral class of " silicates and Germanates " and then to the Department of " layer silicates ( phyllosilicates ) ," where he along with Pentagonit the unnamed group VIII / H .36 was formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Cavansit also included in the category of " silicates and Germanates " and there in the department of " layer silicates ( phyllosilicates ) ". This division, however, is further divided according to the structure of the layers, so that the mineral is found in accordance with its construction in the subsection " Simple tetrahedral grids with 4, 5, (6) and 8 rings involved " where it is the only member of the unnamed group 9.EA.50 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the Cavansit in the class of " silicates and Germanates " there, however, in the fine already divided the department " layer silicates: Modulated mentals". Here he is with Pentagonit in the group of " vanadium layer silicates " with the system no. 74.03.07 within the subdivision " layer silicates: Modulated layers with joined strips " to find.
Modifications and varieties
The compound Ca [ V4 O | Si4O10 ] · 4H2O is dimorphic and is found in nature in addition to the orthorhombic crystallizing Cavansit even as also orthorhombic, but crystallized in a different space group Pentagonit ago.
Education and Locations
Cavansit forms primarily hydrothermally in cavities of volcanic rocks such as basalt and tuff. Accompanying minerals occur among others analcime, Apophyllite, Calcite, Chalcopyrite, heulandite, native copper, mordenite, Pentagonit, stilbite and Thomsonit.
Known due to exceptional Cavansitfunde are primarily the Zeolite - quarries in the district of Pune (formerly Poona anglicized (h)) in the Indian state of Maharashtra, where radiating aggregates were up to three centimeters in diameter have been found.
Apart from its type locality Owyhee Dam and the only other known locality Goble in the U.S. state of Oregon, the mineral occurred among other things still in the quarry at Municipal Morro Reuter in Brazil and in Aranga in the Kaipara district in New Zealand.
Crystal structure
Cavansit crystallizes in the orthorhombic space group Pcmn ( Raumgruppen-Nr. 62) with the lattice parameters a = 9.79 Å; b = 13.64 Å and c = 9.63 Å and four formula units per unit cell.
Use
Cavansit has no technical- economic importance. Only among collectors it enjoys its bright blue luster due to great popularity.