Mendozite
A variety of Minerals
What is Mendozite?
Mendozite is a sulfate mineral, one of the alum series, with formula NaAl(SO4)2·11H2O. It is a hydrated form of sodium aluminium sulfate (soda alum). It was discovered in western Argentina in 1868, probably near San Juan. The exact location has been lost, but was described as "San Juan, near Mendoza", and it is the latter city that give the mineral its name. It occurs in evaporites, presumably from the oxidation of sulfide minerals in the presence of clays. It is very soluble in water, and so can only be found in dry regions: however, in can still effloresce (lose water of crystallisation) in extremely arid climates, altering to tamarugite (the hexahydrate).
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Mendozite 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.
Quick Facts
Physical Properties
- Color
- Colourless (turns white upon exposure); colourless in transmitted light.
- Hardness (Mohs)
- 3
- Rock tumbling
- Not recommended
Chemical Properties
- Chemical Formula
- NaAl(SO4)2 · 11H2O
- Elements
- Al, H, Na, O, S
Also Known As
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Mendozite FAQs
How do I identify Mendozite?
Mendozite can be identified by its hardness of 3 on the Mohs scale, Colourless (turns white upon exposure); colourless in transmitted light. color. Look for these key characteristics when examining specimens.
What color is Mendozite?
Mendozite typically appears in Colourless (turns white upon exposure); colourless in transmitted light.. Color can vary depending on impurities and formation conditions.
How hard is Mendozite?
Mendozite has a hardness of 3 on the Mohs scale. This makes it a soft mineral that can be scratched easily.
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