Which rock is an example of mantle-derived igneous rock commonly cited in diamond-bearing contexts?

• A. Peridotite
• B. Marble
• C. Sandstone
• D. Schist

Answer: (A)

Understanding where diamonds come from means recognizing rocks formed in the mantle. Diamonds crystallize under high pressure deep in the mantle, so the mantle’s igneous rocks are the ones you’d expect to be linked to diamond contexts. Peridotite is a primary mantle rock, ultramafic in composition and rich in olivine and pyroxene, representing the kind of material that makes up the upper mantle. In diamond-bearing settings, you often find mantle material as xenoliths or as part of kimberlite plumbing, which is why peridotite is frequently cited when discussing their origin. The other options don’t fit this mantle-igene origin: marble is metamorphosed carbonate rock, sandstone is sedimentary, and schist is metamorphic.