Question

what is a mineral's estimated hardness if it can scratch a fingernail, penny, steel plate, and glass?

Answer 1

5.5

Step-by-step explanation:

Answer 2

5.5

Step-by-step explanation:

Instead, common objects are used as tools to perform the hardness test: fingernail (hardness = 2.5) copper penny (hardness = 3) glass plate or steel knife (hardness = 5.5)