The following is a wikipedia entry about cavansite:
Cavansite
Article
Talk
Read
Edit
View history
Tools
From Wikipedia, the free encyclopedia
Cavansite
Cavansite-121680.jpg
Cavansite on heulandite
General
Category Silicate mineral
Formula
(repeating unit) Ca(VO)Si4O10·4(H2O)
IMA symbol Cav[1]
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H–M Symbol: (2/m 2/m 2/m)
Space group Pcmn
Unit cell a = 9.792(2) Å,
b = 13.644(3) Å,
c = 9.629(2) Å; Z = 4
Identification
Color Brilliant sky-blue to greenish blue
Crystal habit Radiating acicular prismatic crystals commonly as spherulitic rosettes
Cleavage Good on {010}
Tenacity Brittle
Mohs scale hardness 3 - 4
Luster Vitreous, pearly
Streak Bluish-white
Diaphaneity Transparent
Specific gravity 2.25 - 2.33
Optical properties Biaxial (+)
Refractive index nα = 1.542(2) nβ = 1.544(2) nγ = 1.551(2)
Birefringence δ = 0.009
Pleochroism Visible: X=Z= colorless Y= blue
2V angle Measured: 52°
References [2][3][4][5]
Cavansite, whose name is derived from its chemical composition, calcium vanadium silicate, is a deep blue hydrous calcium vanadium phyllosilicate mineral, occurring as a secondary mineral in basaltic and andesitic rocks along with a variety of zeolite minerals. It's blue coloring comes from vanadium, a metal ion.[6] Discovered in 1967 in Malheur County, Oregon, cavansite is a relatively rare mineral. It is polymorphic with the even rarer mineral, pentagonite. It is most frequently found in Pune, India and in the Deccan Traps, a large igneous province.
Uses of cavansite
Although cavansite contains vanadium, and could thus be a possible ore source for the element, it is not generally considered an ore mineral. However, because of its rich color and relative rarity, cavansite is a sought-after collector's mineral.
Associated minerals
Members of the apophyllite group
Members of the zeolite group, particularly stilbite
babingtonite, Ca2Fe2Si5O14OH
quartz, SiO2
calcite, CaCO3
pentagonite, Ca(VO)Si4O10 · 4(H2O)
Notes for identification
Cavansite is a distinctive mineral. It tends to form crystal aggregates, generally in the form of balls, up to a couple centimeters in size. Sometimes the balls are coarse enough to allow the individual crystals to be seen. Rarely, cavansite forms bowtie-shaped aggregates. The color of cavansite is distinctive, almost always a rich, bright blue. The color is the same as its dimorph, pentagonite, but the latter is generally much more spikey with bladed crystals. Finally, the associated minerals are useful for identification, as cavansite is frequently found sitting atop a matrix of zeolites or apophyllites.