There are various ways that geologists use for identification of minerals. These methods or tests are very simple to perform and can quickly help in the accurate identification of minerals. We will discuss here only three of them.
1) Hardness:
It is the property of a mineral that resists its scratching. It has something to do with the chemical bonding between atoms of a mineral. The stronger that bonding is, the difficult it is for you to scratch the mineral. Although presence of impurities can effect the right diagnosis of the mineral but still hardiness is a very good criteria to identify a mineral. For example, lead has very low hardness due to which we can write through it on paper, however a steal nib would never let us write because it has good hardness and it cannot be scratched easily. Please see the attached image, it shows hardness values of different minerals that give unique identification to them.
2)Streak:
It is the test in which mineral is scraped with a porcelain piece. This streaking can help in the diagnosis of the mineral in powdered form. For example, when chromite is streaked it gives choclate brown streaks and it is the color very different from all other minerals and it can be quickly identified.
3) Physical properties:
There are some ways of identifying a mineral by just looking at them, however some experts are better at it then some one who has zero experience. This is because minerals have some characteristics like color, luster (that can be metallic or non metallic) and taste or smell. For example, sulfur has a specific smell and it is quickly identified with it. Chalcanthite has a specific taste and it can be quickly identified with it.
Hope it helps!
