Garnet is any of a group of silicate minerals generally associated with metamorphic and some igneous rocks. They come in a variety of compositions, the most common of which is almandine (Fe₃Al₂(SiO₄)₃) and pyrope Mg₃Al₂(SiO₄)₃, which are often red in colour and occurs as large twelve sided crystal with diamond-shaped faces. It has a mineral hardness of 6.5-7.5 for almandine and 7-7.5 for pyrope on Mohs' scale; a vitreous luster; fractures conchoidally with no cleavage; and is commonly transparent. 

   Garnets of pyrope-almandine composition occurs at Aswan, in the Eastern desert, at Kharga Oasis, and the Sinai. Aswan is most likely the main source of this mineral, since the other sites have mineral grains of too small a size. Garnets were mainly used by the ancient Egyptians for beads starting in the Predynastic period, and during part of the Middle kingdom for both beads and inlay. It was also used during the Second Intermediate and New Kingdom periods (Lucas and Harris, 1962).

References

Lucas, A. & Harris, J.R. (1962) Ancient Egyptian materials and industries. E. Arnold, London, 523 p.
 
 

a) Misc objects

Middle Kingdom period (12th Dynasty) pectoral with the name of Senwosret II made of gold, carnelian, feldspar, garnet, and turquoise (lenght: 8.3 cm: Metropolitan Museum of Art, New York).

b) Inlay

New Kingdom period (late 18th Dynasty) stained ivory prancing horse with inlay of garnet eyes (length: 15 cm: Metropolitan Museum of Art, New York).