Commercial Terminology


Don’t be surprised if you see gneiss labeled as “granite” at a cabinet shop or monument company. In the dimension stone trade, any rock with visible, interlocking grains of feldspar is considered to be “granite” in that industry.

Seeing gneiss, gabbro, labradorite, diorite, and other types of rock marketed as “granite” disturbs many geologists. However, this long-time practice of the dimension stone trade simplifies discussions with customers since not everyone knows the technical names of unusual igneous and metamorphic rocks.

corundum gneiss with sapphire
Corundum Gneiss: This is a specimen of corundum gneiss from Gallatin Valley, Montana. This specimen is about four inches across and has a round blue sapphire crystal on the left side.

Leave a Reply

Your email address will not be published. Required fields are marked *