Both of these colors are close to black but they aren't black.  They are a dark charcoal gray.

Differences between Iron Ore and Peppercorn.

Iron Ore has green undertones while Peppercorn has blue and purple undertones.

Peppercorn has an LRV of 10 while Iron Ore has an LRV of 6.

Here are some color palettes for each color that you can use in your space.

For more paint color comparisons go to At Lane and High.