FLUORITE
Fluorite is a calcium fluoride mineral (CaF2).
The most diagnostic physical property of fluorite is its hardness
(H≡4). Fluorite typically forms cubic crystals and, when broken,
displays four cleavage planes (also quite diagnostic). When broken under
controlled conditions, the broken pieces of fluorite form double pyramids (see
below). Fluorite is a good example of a mineral that can be any
color. Common fluorite colors include clear, purple, blue, green, yellow,
orange, and brown. The stereotypical color for fluorite is purple.
Purple is the color fluorite "should be". A mineral collector
doesn't have fluorite unless it's a purple fluorite.
Fluorite occurs in association with some active
volcanoes. HF emitted from volcanoes can react with Ca-bearing rocks to
form fluorite crystals. Many hydrothermal veins contain fluorite.
Much fluorite occurs in the vicinity of southern Illinois (Mississippi Valley-type
deposits).
Fluorite
samples showing dioctahedral cleavage (4 cleavage planes & double pyramid
shape); yellow fluorite is 11 mm across; clear & green fluorites are 14 mm
across each; purple fluorite (not black!) is 12 mm across.
Fluorite
in dolostone (Lockport Dolomite, upper Niagaran Series, Wenlockian, upper
Middle Silurian; Graymont Dolime Inc. quarry at Genoa, northwestern Ottawa
County, northwestern Ohio, USA). Collected 2007 by John Vasichko and
Joseph Vasichko.
Fluorite
(purple mass) in a dolomitized stromatoporoid (Animalia, Porifera,
Stromatoporoidea), derived from the Detroit River Group (Lower-Middle Devonian)
or lower Dundee Formation (Middle Devonian) at Stoneco Auglaize Quarry, just
southeast of town of Junction, Auglaize Township, northeastern Paulding County,
northwestern Ohio, USA. Specimen owned by Wayne Snyder.
Fluorite
(purplish) & galena (silvery-gray) from the Denton Mine, Hardin County,
Illinois, USA.
Fluorite
from the Rosiclare Level, Cross-Cut Ore Body, Minerva # 1 Mine, Cave-in-Rock
Mining District, southern Illinois, USA. Owned by Ross Lillie.
Fluorite
from the Rosiclare Level, Cross-Cut Ore Body, Minerva # 1 Mine, Cave-in-Rock
Mining District, southern Illinois, USA. Owned by Ross Lillie.
Fluorite
from the Rosiclare Level, Cross-Cut Ore Body, Minerva # 1 Mine, Cave-in-Rock
Mining District, southern Illinois, USA. Owned by Ross Lillie.
Fluorite
from the Rosiclare Level, Cross-Cut Ore Body, Minerva # 1 Mine, Cave-in-Rock
Mining District, southern Illinois, USA. Owned by Ross Lillie.