Katoite

A variety of Minerals

What is Katoite?

Pricing varies for every rock and mineral, so use these universal factors to gauge Katoite 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.

Applies to all rocks & minerals.

See where Katoite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

Map preview

North ZoneCentral RidgeSouth Basin

Chemical Formula: Ca₃Al₂[◻(OH)₄]₃ The formula for general "hydrogrossular" is derived by the progressive exchange of grossular's Si with vacancies (◻), while maintaining local charge balance by attaching one H+ to each of the four adjacent oxygens (so 4H+ in total) per each one Si⁴⁺ lost. This progressive exchange can also be represented as Ca₃Al₂(SiO₄)^3-x(OH)₄x. In end-member katoite, the replacement is complete (so x = 3). Previously, the mineral "hibschite" (no longer an IMA-approved species) was considered an intermediate member of the grossular-katoite series, and was defined as Ca₃Al₂(SiO₄)^3-x(OH)₄x, where x = 0.2-1.5; compositions where x < 0.2 were still considered grossular, whereas compositions where x > 1.5 were considered katoite. Now, based on the modern "50% rule", what was previously called "hibschite" would now be considered grossular (or perhaps more descriptively as "OH-bearing grossular"), although "hibschite", "hydrogrossular" and "hydrogarnet" are still all informally in common use.
Elements: Al, Ca, H, O