How do I identify Katoite?

Katoite can be identified by its hardness of 5 - 6 on the Mohs scale, Colourless color. Look for these key characteristics when examining specimens.

What color is Katoite?

Katoite typically appears in Colourless. Color can vary depending on impurities and formation conditions.

Katoite has a hardness of 5 - 6 on the Mohs scale. This gives it moderate hardness.

A variety of Minerals

Estimate the market value of Katoite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

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

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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