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| Chemistry:
KAl(SO4)2·12(H2O) [Hydrated
Potassium Aluminum Sulfate] | Discovered
in 1875;
IMA
status: Valid (pre-IMA; Grandfathered). Potassium
Alum is named for its content of the element potassium (K) and the Latin, alumen. |
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Classification
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Mineral
Classification: |
Sulfates |
Strunz 8th
Ed. ID:
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6/C.14-20
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Nickel-Strunz 10th
Ed. ID:
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7.CC.20 |
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7 : SULFATES (selenates, tellurates, chromates, molybdates,
wolframates) C : Sulfates (selenates, etc.) without additional anions, with
H2O C : With medium-sized and large cations
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Related
to: |
Alum
Group. Sodium Alum - Zincovoltaite Series.
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Crystal
Data
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Crystallography:
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Isometric
- Diploidal
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Crystal
Habit:
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Rarely
as tiny octahedral crystals, if precipitated from pure water solution; cubic from
alkaline solutions. Commonly stalactitic, columnar, granular, or massive efflorescences.
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Twinning:
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Very rare;
on [111]
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Physical
Properties
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Cleavage: |
[111]
Poor/Indistinct
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Fracture: |
Conchoidal
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Tenacity:
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Brittle
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Hardness
(Mohs): |
2.0
- 2.5
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Density:
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1.757 (g/cm3)
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Luminescence:
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None |
Radioactivity:
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Barely
Detectable;
GRapi = 124.32 (Gamma Ray American Petroleum Institute Units)
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Other: |
Soluble in water
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Optical
Properties
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Color: |
Colorless,
White
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Transparency: |
Transparent
to Translucent |
Luster: |
Vitreous |
Refractive
Index: |
1.456
Isotropic
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Birefringence: |
None
(Isotropic); may be weakly anomalously birefringent
and sectored
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Dispersion: |
n/a |
Pleochroism: |
None |
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Occurances
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Geological
Setting: |
Formed
from argillaceous rocks or coal containing oxidizing
pyrite or marcasite; may be a fumarolic or solfataric
precipitate. |
Common
Associations: |
Alunogen,
Gypsum, Epsomite, Melanterite, Pickeringite, Sulfur |
Type
Locality: |
Possibly
Alum Grotto, Porto Levante, Vulcano Island, Eolie Islands
(Aeolian Islands), Lipari, Messina Province, Sicily,
Italy |
Year
Discovered: |
1875
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View
mineral photos: |
Potassium
Alum
Mineral Photos and Locations |
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More
Information
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|
Mindat.org Webmineral.com |
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Potassium
Alum (also known as Alum-K) is an extremely rare sulfate
mineral that is very rarely available as a faceted gem.
It is a very unusual mineral in that it is both barely
radioactive
and water
soluble.
There
are very few localities to find gem quality crystals
of Potassium Alum. A few of these are the El Desierto mine, San Pablo de Napa, Daniel Campos
Province, Potosí Department, Bolivia; Alaunhöhle, near Dresden, Saxony, Germany;
Alum mine, Alum District, Esmeralda County, Nevada,
USA; Alum King Mine, Marysvale District (Marysvale Uranium
area), Piute County, Utah, USA.
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Potassium
Alum
gems for sale:
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have not photographed our Potassium
Alum
gems. Please
check back soon.
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