What is the most unreliable source to identify a minerals property?

The most unreliable source is Color. This is unreliable because stones and minerals are always exposed to a lot of properties. For example, when the mineral is exposed to weathering, it is already expected that the stones and minerals will suddenly change its color.

In order to check the type of mineral available, streak can be referred to in order to know the actual color of the mineral that is being identified. Hardness is a reliable source and this is one of the characteristics that are checked by professionals to determine the type of mineral available. Luster may be used from time to time.