Garnet group
Al 1%, Ca 1%, Cr 1%, Mg 1%, Mn 1%,

estimated elemental composition and molecular weight 
Minerals with the same name may vary widely in appearance and composition, and very few are >99% (reagent grade) pure.

Gram formula weight (molecular mass) = 198.29

Minerals may vary in elemental composition and impurity levels. The formula given is an approximation.
Wikipedia Page:

Garnet group
is defined with respect to the entities below:
The entities below are defined with respect to:
Garnet group
Mineral (generic)

chemical compound molecule metal molecular science reaction mechanism ionic material acid base geometry reactivity synthesis science knowledge chemistry Lewis