The garnet group of minerals is a group of chemically and physically similar minerals.  They are as follows:

Grossularite is a calcium aluminum silicate. It can be colorless, gray, many shades of yellow and green, also pink, red, brown and black.
Pyrope is a magnesium aluminum silicate.  Colors are blood-red, dark red, purplish-red, orangish-red and pinkish -red.
Spessartite is a manganese aluminum silicate, and can be orange, reddish-orange, red, reddish-brown, yellowish-brown and brown.
Almandite is an iron aluminum silicate, Almandine is typically a deep red-violet, also can be red, brownish-red and brownish-black.
Andradite is a calcium iron silicate. It occurs in yellowish-green, green, greenish-brown, gray and black.
Uvarovite is a calcium chromium silicate; the color is dark green. 

The uses of garnet are as gemtones and abrasives.  Because they are hard, lack cleaveage and fracture into sharp, irregular pieces, garnets are an excellent abrasive.  As a gemstone, they highly refractive, hard, have beautiful colors, and are transparent.  However, possibly due to their abundance and widespread use, they do not fetch a high price as a gemstone.