Question

Trace amounts of impurity in a mineral can commonly produce significant differences in among individual crystals of this mineral

Answer 1

I think you meant "...differences in _________ among individual..."
In this case, the answer you are looking for is COLOR. 

Answer 2

Trace amounts of impurity in a mineral can commonly produce significant differences in color among individual crystals of this mineral.

What is Impurity?

These are chemical substances which are found in minerals and usually have a different composition.

Impurities brings about varying differences among individual crystals of mineral which is why the impurities have to be removed in order to get a pure substance which possesses the unique properties of the mineral.

Read more about Impurity here https://brainly.com/question/4378347