Which statement about diamonds and carbon is true according to the formation environment?

Which statement about diamonds and carbon is true according to the formation environment?

• A. Diamonds form in carbon-poor environments
• B. Diamonds require high temperatures but not carbon
• C. Diamonds form where there is carbon available
• D. Diamonds form only in the presence of nickel catalysts

Answer: (D)

Diamonds form where there is carbon available, under the high-pressure, high-temperature conditions found deep in Earth's mantle. The carbon source is essential; without carbon, diamond cannot form. Nickel catalysts are used in some laboratory methods to promote diamond growth, but natural diamond formation does not depend on nickel catalysts. So the claim that diamonds form only in the presence of nickel catalysts isn’t accurate for natural formation. The key idea is that carbon availability under the right pressure–temperature environment is what enables diamond crystallization.

Diamonds form where there is carbon available, under the high-pressure, high-temperature conditions found deep in Earth's mantle. The carbon source is essential; without carbon, diamond cannot form. Nickel catalysts are used in some laboratory methods to promote diamond growth, but natural diamond formation does not depend on nickel catalysts. So the claim that diamonds form only in the presence of nickel catalysts isn’t accurate for natural formation. The key idea is that carbon availability under the right pressure–temperature environment is what enables diamond crystallization.