👉 The term "kilhamite" is a mineral in the group of minerals called mica. Mica is a silicate that forms as a crystalline solid, and its chemical formula is CaSiO3. Kilhamite is a type of mica with a hexagonal crystal structure. It has a hardness of 1-2 on the Mohs scale, which means it is not very hard but still strong enough to be used in certain applications.