Final answer:
Topaz, with a Mohs hardness of 8, has the greatest hardness among the minerals listed, making it the hardest compared to feldspar, calcite, and gypsum. The Mohs scale is used to determine the relative hardness of minerals.
Step-by-step explanation:
The Mohs hardness scale is a qualitative tool used to determine the hardness of minerals. On this scale, different minerals are ranked according to their ability to resist abrasion or scratching. The correct answer to which mineral has the greatest hardness on the Mohs hardness scale among the options provided is D) topaz. Other minerals mentioned in the question have lower hardness values: feldspar has a typical Mohs hardness of around 6-6.5, calcite around 3, and gypsum 2. Topaz, however, has a hardness of 8 on the scale, making it the hardest among the listed minerals. When identifying mineral hardness in the classroom, you can use common objects with a known hardness available on the scale to scratch test the minerals and thereby identify their relative position on the scale.
Answer: D) topaz