This garnet has the general composition (Mg,Fe,Mn,Ca)3
(Al,Fe,Cr)2(SiO4)3 but garnet refers to a group of minerals with TO4 groups where T = Si, As, V, Al, Fe, Te. They are found in many rock types.
This sample is described as garnet amphibolite. It has inclusions of garnet which are 10-12 cm across. The sample is on display in the Smithsonian Museum of Natural History.
The garnet family includes 15 minerals with the same basic atomic configuration but different chemical compositions. The name garnet comes from the Latin word for "pomegranate". Garnets were thought to resemble the fruit's seeds. Small, dark red garnets have been used widely in jewelry, and that color is common in garnets, but they have been found in all colors except blue.