What differentiates one mineral group from others? Why are minerals grouped in this manner rather than using their properties?
1 Answer
Primarily it's the chemistry of the minerals. Following this is the crystal structure of the minerals.
Explanation:
Minerals are primarily grouped by their chemical composition, in one of the following categories:
Natives - these are single element minerals, like gold and silver.
Silicates
Oxides
Halides
Hydroxides
Carbonates
Sulfides
Sulfates
Phosphates
Some minerals share the shame chemical composition (polymorphs), so the chemical composition alone is enough to uniquely group them. This is an example of when crystal structure is necessary to group some minerals (examples are the aluminosilicates kyanite, andalusite, and sillimanite).
The properties of minerals are not enough to uniquely separate them into groups, since so many minerals share the same properties. Organization would be very difficult, and it would lead to too many groups. In addition, many minerals have variations in their physical properties, making it even more difficult to accurately group them into a set group. Going further, optical mineralogy opens up a new bucket full of different diagnostic features, further complicating this matter.
