Concept:
Moh's scale of hardness ranks minerals from \(1\) to \(10\) based on their ability to scratch other minerals.
Step 1: On Moh's scale:
\[
1=\text{Talc}
\]
which is the softest mineral.
Step 2: The highest hardness value on Moh's scale is:
\[
10
\]
Step 3: Diamond has hardness:
\[
10
\]
Step 4: Therefore, diamond is the hardest mineral on Moh's scale.
Hence,
\[
\boxed{\text{Diamond}}
\]