This is a tricky question! It depends on what kind of stone and metal you're talking about.

Here's why:

* Hardness is measured on a scale: The Mohs Hardness Scale is used to measure the scratch resistance of minerals. Diamond is the hardest known natural mineral, while talc is the softest.

* Metals vary in hardness: Some metals like gold and silver are relatively soft, while others like steel and titanium are much harder.

* Stones also vary in hardness: A diamond is significantly harder than a piece of chalk.

Examples:

* Diamond (stone) is much harder than most metals.

* Steel (metal) is harder than granite (stone).

So, there's no simple answer. You need to be specific about the type of stone and metal to determine which is harder.