Plazolite

Plazolite is a hydrous aluminum garnet (a hydrogrossular) in which hydroxyl groups substitute for part of the silica. It was originally described as a distinct mineral but is now considered synonymous with hibschite, occupying the same intermediate position in the grossular-katoite series.

It is isometric, typically colorless to white or pale, and occurs as small crystals or granular aggregates in altered calcium-rich rocks.

Plazolite is best known from the classic contact-metamorphic locality at Crestmore, California, where many calc-silicate minerals were first found or well studied.

Plazolite (hydrogrossular) forms by low-temperature hydrothermal and contact-metamorphic alteration of calcium-aluminum-rich rocks, such as limestones intruded and altered by igneous bodies.

The hydrogarnet substitution is promoted by water-rich, lower-temperature conditions. It grows with other calc-silicates including vesuvianite, diopside, grossular, and calcite.

The type occurrence is the Crestmore quarries in Riverside County, California, a renowned source of contact-metamorphic and skarn minerals.

Look for small colorless to white isometric garnet crystals or granular material in skarn and contact-metamorphic calc-silicate rock. Hardness is about 6-7 with a pale streak and vitreous luster.

Because plazolite is equivalent to hibschite, separating it from grossular and other hydrogarnets requires measuring the hydroxyl-for-silica substitution. Its pale color and skarn setting distinguish it from common colored garnets, but analysis is needed for definitive identification.

Plazolite has no gem or industrial use; it is a collector and research mineral. Historically it is significant as one of the well-characterized hydrogrossular species from Crestmore, contributing to the understanding of the hydrogarnet series.

Specimens are valued by collectors of California minerals and garnet-group species. It has no distinct metaphysical tradition.