Magnesium is somewhat abundant, but less so than calcium. It is one of the bases of dolomite and magnesian limestone, and is an ingredient of talc and all talcose rocks.
The substances now enumerated constitute nearly the entire mineral mass of the crust of the earth. They may be arranged in the following order:—
I. NON-METALLIC SUBSTANCES.
| Oxygen. Carbon. | Hydrogen. Sulphur. Fluorine. | Nitrogen. Chlorine. |
II. METALS.
| Iron. | Manganese. |
III. METALLIC BASES OF THE EARTHS AND ALKALIES.
| Silicium. Sodium. | Aluminium. Calcium. | Potassium. Magnesium. |
These substances, chemically combined, form Simple Minerals.