A combination of elements Magnesium (Mg) and Silicon (Si) and 3 atoms of Oxygen (O). [I actually knew that from the top of my head... surprising...] I'm not sure of the exact name, but look around Wikipedia, and you might find it :]
MgSiO3 is the formula for Enstatite, a rock forming mineral (common in igneous and metamorphic rock).
Zinc Silicite
SnSiO3 is stannous silicon oxide.