Answer the following question given this paragraph: 

Color is probably the easiest property to observe. Unfortunately, you can rarely identify a mineral only by its color. Sometimes, different minerals are the same color. For example, you might find a mineral that is a golden color and think it is gold. But it might actually be pyrite, or “fool's gold,” which is made of iron and sulfide. It contains no gold atoms.


Q: Although it is the easiest to observe, what property is not ideal as a sole way to identify minerals?


A:
color