Mineral Resource of the Month: Garnet

by U.S. Geological Survey
Tuesday, January 15, 2019

Wollastonite with embedded andradite garnet ore from New York. Credit: Kenneth C. Curry.


Geologic Occurrence

Garnet is the general name given to a group of complex silicate minerals, all with isometric crystal structure and similar properties and chemical composition. The most common garnet minerals are classified into three groups: the aluminum-garnet group, the chromium-garnet group and the iron-garnet group. Worldwide, garnet resources are large and occur in a wide variety of rocks, principally in metamorphic rocks such as gneisses and schists. Garnet also occurs in veins, contact metamorphic rocks, metamorphosed crystalline limestones, pegmatites and serpentinites. In addition, alluvial garnet sands are associated with heavy-mineral sand and gravel deposits in many parts of the world.

U.S. Production and World Production

Credit: K. Canter, AGI.

2017 World Production

Credit: K. Canter, AGI.


U.s. Industrial Garnet Imports

Credit: K. Canter, AGI.

Waterjet-grade industrial garnet on the left and abrasive blasting garnet on the right. Credit: Kenneth C. Curry.

Commercial Usage

Garnet that exhibits good clarity, color and size is used as a gemstone. Garnet that does not meet gem-quality standards is used for industrial applications. Garnet has many industrial applications because of its angular fractures, relatively high hardness and specific gravity, chemical inertness, nontoxicity, lack of associated crystalline silica, and ability to be recycled. The primary applications include use in waterjet cutting, abrasive blasting media, water filtration and abrasive powders. A few of the domestic industries that consume garnet include aircraft and motor vehicle manufacturing and ceramics and glass production.

Fun Facts

Although garnet crystals most commonly occur with a reddish hue, garnets also can occur in many other colors, including blue, brown, green, orange, purple and yellow.

Industrial garnet has a high enough hardness to cut through many materials, such as metals, at extremely high speeds. Industrial garnet is considered the industry standard abrasive in waterjet cutting.

Visit minerals.usgs.gov/minerals for more information

design by K. Cantner and N. Schmidgall, AGI

Credit: U.S. Geological Survey

Credit: American Geosciences Institute

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