Alum-(k)
Alum-(K)
A variety of Minerals
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What is Alum-(k)?
Alum-(K) is a hydrous potassium aluminium sulfate mineral with formula KAl(SO4)2·12(H2O). It is the mineral form of potassium alum and is referred to as potassium alum in older sources. It is a member of the alum group. It occurs as colorless to white, soft isometric crystals and efflorescence coatings. Rare crystals are octahedral in form if occurring as precipitates from neutral water solution, but cubic in form if the solution is alkaline. It occurs as a precipitate around volcanic fumaroles and solfataras. It also occurs as an alteration in argillaceous sediments or coal beds which contain oxidizing sulfide minerals (pyrite or marcasite). Occurs associated with alunogen, pickeringite, epsomite, melanterite, gypsum and native sulfur. Occurrences include Mount Vesuvius, Italy and Alum Cave, Sevier County, Tennessee.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Alum-(k) before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Alum-(k) Localities Map
See where Alum-(k) is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- Colourless, white; colourless in transmitted light.
- Hardness (Mohs)
- 2
- Density
- 1.753 g/cm³
Chemical Properties
- Chemical Formula
- KAl(SO4)2 · 12H2O
- Elements
- Al, H, K, O, S
Also Known As
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Alum-(k) FAQs
How do I identify Alum-(k)?
Alum-(k) can be identified by its hardness of 2 on the Mohs scale, Colourless color. Look for these key characteristics when examining specimens.
What color is Alum-(k)?
Alum-(k) typically appears in Colourless, white; colourless in transmitted light.. Color can vary depending on impurities and formation conditions.
How hard is Alum-(k)?
Alum-(k) has a hardness of 2 on the Mohs scale. This makes it a soft mineral that can be scratched easily.
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