A mineral determined by using fingernailpenny or nail?

A mineral can be tested for hardness using a fingernail, penny, or nail, which are common items that serve as reference points on the Mohs scale of mineral hardness. For instance, a fingernail has a hardness of about 2.5, while a copper penny is around 3.5. If a mineral can be scratched by a fingernail, it is softer than 2.5; if it can be scratched by a penny but not a fingernail, it falls between 2.5 and 3.5. This simple test helps in identifying the mineral's hardness and assists in classification.