It's not quite accurate to say there are only four main mineral groups. There are actually eight main mineral groups based on the anion group (the negatively charged ion) present in the mineral's chemical formula.

Here are the eight main mineral groups:

1. Silicates: This is the largest and most important mineral group, making up about 90% of the Earth's crust. They contain silicon and oxygen, often in combination with other elements. Examples: Quartz, Feldspar, Mica.

2. Carbonates: These minerals contain the carbonate ion (CO3)2-. They are often found in sedimentary rocks. Examples: Calcite, Dolomite.

3. Oxides: These minerals contain oxygen bonded to a metal. Examples: Hematite, Magnetite, Corundum.

4. Sulfides: These minerals contain sulfur bonded to a metal. Examples: Galena, Pyrite, Chalcopyrite.

5. Sulfates: These minerals contain the sulfate ion (SO4)2-. Examples: Gypsum, Barite.

6. Halides: These minerals contain a halogen element (fluorine, chlorine, bromine, or iodine) bonded to a metal. Examples: Halite (rock salt), Fluorite.

7. Phosphates: These minerals contain the phosphate ion (PO4)3-. Examples: Apatite.

8. Native Elements: These minerals are composed of a single element. Examples: Gold, Silver, Copper, Diamond (carbon).

While these are the eight main groups, some mineralogists prefer to further subdivide these groups or include other less common groups.