Final answer:
To derive a hardness number via a pyramid indentation test in an engineering context, methods like the Vickers or Brinell tests are used; these aren't directly related to the Mohs hardness scale. In a classroom, the Mohs scale can be used to estimate mineral hardness by using common objects with known hardness values for scratch-testing.
Step-by-step explanation:
The hardness number in a square pyramid indentation test is not derived using the Mohs scale of relative mineral hardness directly. Instead, a different test such as the Vickers or Brinell hardness test would be used, where a square pyramid-shaped diamond indenter is pressed into the material. The hardness number is calculated based on the indentation size or depth. However, when identifying mineral hardness in a classroom setting, one can reference the Mohs scale and use common objects with known hardness to scratch-test the minerals. Items listed on the right side of Figure 2.6 can be used to estimate the hardness of unknown minerals by seeing which objects scratch others, allowing us to compare the mineral's hardness to those on the Mohs scale.