Spessartine is a pretty cool mineral and looks great on the new Ladies' J*D dials! It is actually composed of four elements; Manganese, Aluminium (that's Aluminum to our American readers
) Silicon and Oxygen, and has the chemical formula Mn2+3Al2(SiO4)3 (I know you were curious!)
It is named after its primary location, the Spessart Mountains in Bavaria, Germany. Clearly an area now famous for cars, beer and minerals!
It occurs naturally in colors ranging from reddish orange, yellowish brown, reddish brown and brown. It can range from transparent to translucent. It is crystalline, which means it forms fine sized crystals, and massive, in that they easily join together. It is also sub-conchoidal, which means it is brittle and fractures easily. It has a hardness of up to 7.5 (Diamond defines the scale at 10).
Cool image below (stolen from Webmineral.com)