What is the typical characteristic of indicator minerals in relation to diamond exploration?

Indicator minerals are crucial in diamond exploration due to their ability to suggest the presence of diamonds in a given area. These minerals, which are often found in the same geological environments as diamonds, serve as guides for exploration teams. Their presence can indicate that the conditions for diamond formation may have been met in the surrounding rock formations.

These minerals, such as ilmenite, garnet, and chromian spinel, are specifically associated with kimberlite and lamproite pipes—the primary source rocks for diamonds. When geologists find these indicator minerals, they often conduct further studies or sampling to confirm the potential presence of diamonds in that location.

The other options do not capture the essence of why indicator minerals are vital in the exploration process. While some indicator minerals can have value, it's their geological significance that is paramount. They are not universally common in all rock types, nor are they exclusively found in soil; rather, they can be located in various geological formations where diamonds are likely to exist.