PHYSICAL PROPERTIES:
Chemistry: SrSO4
Composition: Strontium Sulfate
Class: Sulfates
Group: Barite
Crystal system: Orthorhombic
Rhombic bipyramidal
Fracture:conchoidal
Hardness: 3 - 3.5
Specific gravity: 3.9
Refractive Index:
Pleochroism:
Luster: vitreous
Streak: white
Cleavage: perfect in one direction
Color: blue but can also be colorless,
yellow to brown or even have tints of
green or red.
Transparency: transparent to translucent.
Associated Minerals: calcite, dolomite,
fluorite, galena, gypsum, strontianite, sulfur and sphalerite.
COMPOSITION:
Celestite has the same structure as Barite (BaSO4),
and forms very similar crystals. Celestite also forms with other colorful
minerals, making very nice combinations. Blue Celestite with bright
yellow sulfur is one of the most famous colorful combinations of minerals.
The idea composition of celestite is: SrO 56.42 % SO3
43.58 %. The blue color of celestite has been attributed to the presence
of minute amounts of gold.
ENVIRONMENT:
Celestite is only rarely an accessory mineral of ore veins which were
formed from warm solutions. It is usually found in sedimentary rocks.
The best occurrences are in cavities in sandstone or in limestone. The
crystals usually form in the cavities and
as geodes.
CRYSTAL DESCRIPTION:
Crystals can be bladed and show two large pinacoid faces
top and bottom with small prism faces forming angles on every side.
There are many variations, but the flattened blades and tabular crystals
are the most common. If the pinacoid faces become diminished or are
absent, the resulting prismatic crystal has a rhombic cross section.
This habit is rather common in specimens from Madagascar. Celestite
can also be nodular, fibrous or granular
TESTS:
The flame test works best to distinguish celestite from
barites, that may be of a similar color.
If the flame is a pale green, it is barite, but if the flame is red,
it is celestite
LOCALITIES:
In the United States large crystals were found in a large limestone
quarry. On Kelley Island, Lake Erie region of Ohio. Celestite was also
found in Kansas, Michigan, New York and the Glen Rose Formation in Texas.
Its color in these occurrences is very often the characteristic blue.
Fine blue crystals are found near Manitou, Colorado, and blue
radiating columnar crystal intergrowths are found at Cripple Creek,
Colorado, in the gold mines. A blue fibrous vein material from Beliwood,
Blair County, Peimsylvania, described in 1791, was the original celestite,
the first discovery of this mineral. Clay Center, Ohio is another
limestone quarry, where pockets are filled with fine blue-to-white bladed
celestite, associated with a brown fluorite and yellowish calcite. Colorless
transparent crystals occur with the colemanite in geodes of the Death
Valley area. Reddish cloudy crystals are found near Toronto, Canada.
In the Sicilian sulfur mines, fine white elongated square crystals,
an inch or so in length are associated with sulfur. These are
the ones mentioned in the composition section of this article. Geodes
with large blue crystals much like those from Kelley Island are found
in Madagascar. Which is where our specimens are from.
USES:
Celestite's popular sky blue color makes it a wonderful
mineral specimen. It is also used
as an ore of strontium. Celestite(strontium sulphate) is used
in fireworks, because of its ability to burn with a bright red flame.
The beautiful red color of most fireworks is caused by adding a strontium
compound to the pyrotechnic mixture. Strontium also has uses in the
chemical and pharmaceutical industries. Like Barite, Celestites heavy
specific gravity makes it useful in rotary drilling mud.
Strontium is also widely used to manufacture glass for use in video
displays like television sets. Almost all of the strontium used in this
type of glass is imported, mostly from Mexico, in the form of the mineral
celestite. Strontium is nontoxic and provides a dense glass that shields
viewers from X-rays generated by the high voltage of cathode ray tubes.
Because strontium is much less toxic than either lead or barium, it
is now used almost exclusively for cathode ray tubes in televisions
and computers.
FACTS & HISTORY:
Celestite derives its name from the Latin term caelestis which means
(of the sky) and refers
to the blue color commonly observed in celestite
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