Rock Group

Metamorphic

Grain Size

The fibrous wollastonite and faceted garnet are coarse grained.

Composition

Wollastonite grows at high-temperature in calcium-silica-rich rocks and hornfels describes metamorphic rocks in which the minerals are randomly arranged. Hornfels rocks are formed by contact metamorphism, which refers to when there is an intrusion of magma in the area which bakes the nearby rocks in situ.

Key Features

Garnets are typically red or brown in colour and this sample has them dotted around the wollastonite as large crystals.