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Angelite (a variety of Anhydrite)
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Discovery year unknown; IMA status: Not Valid (tradename for a variety of Anhydrite)
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Composition: |
Calcium |
29.44 % |
Ca |
41.19 % |
CaO |
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Sulfur |
23.55 % |
S |
58.81 % |
SO3 |
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Oxygen |
47.01 % |
O |
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100.00 % |
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100.00 % |
= TOTAL OXIDE |
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Classification
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Mineral
Classification: |
Sulfates
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Strunz 8th
Ed. ID:
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5/B.04-40
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Nickel-Strunz 10th
Ed. ID:
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7.AD.30
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7 : SULFATES (selenates, tellurates, chromates, molybdates,
wolframates) A : Sulfates (selenates, etc.) without additional anions,
without H2O
D : With only large cations
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Related
to: |
Dehydrated
form of Gypsum. Isostructural
with Ferruccite.
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Members
of Group: |
n/a
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Varieties: |
Angelite,
Bowel Stone, Vulpinite
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Synonyms: |
Anhydrous Gypsum,
Anhydrous Sulfate of Lime, Cube Spar, Karstenite, Muriacite,
Siliceous Anhydrous Gypsum
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Crystal
Data
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Crystallography:
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Orthorhombic - Dipyramidal
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Crystal
Habit:
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Crystals
tabular on {010}, {100}, or {001} or equant with large
pinacoidal faces; elongated along [100] or [001], to
15 cm, with about 40 forms recorded. Typically granular,
nodular, parallel or divergent fibrous, massive.
Contorted concretionary forms (Bowel Stone).
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Twinning:
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Simple
or repeatedly on {011}, common; contact twins rare on
{120}.
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Physical
Properties
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Cleavage: |
Perfect
on {010}, nearly Perfect on {100}, Good to Imperfect
on {001}; yielding
pseudocubic fragments.
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Fracture: |
Irregular/Uneven,
Spintery
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Tenacity:
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Brittle
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Moh's
Hardness: |
3.0
- 3.5 |
Density:
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2.96
- 2.98 (g/cm3)
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Luminescence:
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Occassionally
red under LW UV |
Radioactivity:
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Not
Radioactive |
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Optical
Properties
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Color: |
Light
Blue, light Lylac-Blue, Grayish-Blue |
Transparency: |
Translucent,
Opaque |
Luster: |
Pearly
on {010}, Vitreous to Greasy on {001}; Vitreous on {100}.
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Refractive
Index: |
1.567
- 1.618 Biaxial ( + ) |
Birefringence: |
0.0420
- 0.0440 |
Dispersion: |
Strong;
r < v |
Pleochroism: |
None
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Occurances
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Geological
Setting: |
A
major component in sedimentary evaporite deposits and
in the cap rocks above salt domes, commonly formed by
dehydration of gypsum; in igneous rocks, fumarolic deposits,
and in seafloor hydrothermal chimneys, also an alteration
product in hydrothermal mineral deposits.
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Common
Associations: |
Gypsum,
Halite, Sylvite, Polyhalite, Dolomite, Calcite, Magnesite,
Celestine, Sulfur
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Common
Impurities: |
Sr,
Ba, H2O
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Type
Locality: |
Unknown
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Year
Discovered: |
Unknown
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View
mineral photos: |
Angelite
Mineral Photos and Locations |
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More
Information
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Mindat.org
(Angelite) Mindat.org
(Anhydrite) Webmineral.com
(Anhydrite) |
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Angelite
is a trade name for a translucent to opaque, light blue variety
of Anhydrite marketed as a gem material. Angelite
is
named for its "angelic"
light blue to lilac-blue color. Anhydrite
is named from the Greek word anhydros meaning without water, in
allusion to the lack of water in its composition, in contrast to Gypsum,
which contains water. Angelite is a trade name for Anhydrite material with an "angelic" light blue or lilac-blue color.
Anhydrite is a relatively common sedimentary mineral that is the
result of dewatering of the rock forming mineral Gypsum. Good crystal specimens of Anhydrite
are extremely rare so faceted gems are also extremely
rare. However, fine semi-translucent to opaque specimens of Angelite have been
found in Mexico and Peru that have a fine blue color.
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Angelite
gems for sale:
We
have not photographed our Angelite
gems yet. Please
check back soon!
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