Carbonates

The carbonates are compounds which contain one or more metallic elements plus the carbonate radical (CO₄). Most are lightly colored and transparent when pure. All carbonates are soft, brittle, and effervesce, meaning they bubble up, when exposed to warm hydrochloric acid.

The carbonates can be divided as follows:

Calcite Group - The calcite group contains carbonates with an identical crystal structure. All minerals in this group crystallize in the trigonal sect of the hexagonal system, and very commonly form rhombohedrons and scalenohedrons. All the minerals in this group have perfect cleavage, and exhibit a very strong double refraction in transparent rhombohedrons. Minerals in this group can partially or fully replace one another. For example, iron may take the place of magnesium in Magnesite (MgCO₃), transforming it to Siderite (FeCO₃).

Aragonite Group - This group contains structurally related carbonates that crystallize in the orthorhombic system. The minerals in this group frequently form pseudohexagonal trillings. All the members of this group exhibit good cleavage, but not as good as the minerals that are in the calcite group.

Other Carbonates - All carbonates that are not classified in the calcite or aragonite groups.

In many references, the Nitrates and Borates are considered a subcategories of the carbonates.

• Back to carbonate group list (all)
• Back to carbonate group list (subdivided)
• Back to carbonate group list (Dana)