Question

which mineral has a metallic luster, does not react with hydrochloric acid, and has a hardness of 6?
mineral | gold | pyrite
color | golden yellow | yellowish gray to gray
streak | yellow | black
reacts with hydrochloric acid | no | no
hardness | 2.5 - 3 | 6 - 6.5

Explanation:

Match the given criteria (metallic luster, no reaction with hydrochloric acid, hardness of ~6) to the mineral data:

1. Gold has a hardness of 2.5-3, which does not match 6.
2. Pyrite has a hardness of 6-6.5 (close to 6), does not react with hydrochloric acid, and has a metallic luster, so it fits all criteria.

Answer:

Pyrite