Hardness is a property that leads to the identification of the mineral. If the hardness is known, the purpose for which the mineral could be used for, could be identified. For example, talc is used in talcum powder, garnets as abrasive in sandpaper, diamond for cutting tools and so on.
A German mineralogist called Friedrich Mohs devised a scale for measuring hardness. According to his scale, hardness could also be termed as the resistance offered by the mineral to get scratched. Scale rates the hardness of the minerals with values ranging from 1 to 10. Mineral with rating 1 is most soft and rating 10 is the hardest one.
From the Mohs scale rating, we see that talc is very soft and diamond is the hardest mineral. The scale helps identify the resistance of different minerals to get scratched by these ten reference minerals, thereby helps determine the use they be put to. For example, if mineral A is harder than mineral B, then A can scratch B. This means a mineral with a given hardness rating will scratch other minerals of same or lesser hardness. It is found that gemstones like Gold, Silver and Platinum have rating from 2.5 – 4. That is the reason jewelry made out of them are wrapped separately in silk or paper as these gemstones may scratch each other.