Updated as of June 2026
Black Diamond vs Onyx
| Black Diamond | Onyx | |
|---|---|---|
| Price / carat | $200 to $3,000 | $3 to $40 |
| Hardness (Mohs) | 10 | 6.75 |
| Color | Black | Black, White, Banded |
| Treatment | Irradiation or heat (most stones treated black) | Dyeing (most black onyx) |
The bottom line
Black Diamond and Onyx both make beautiful jewelry. Choose by the look you want first, then weigh hardness against how hard you will wear the piece, and let price settle close calls. Read the full guides for Black Diamond and Onyx.
Frequently asked questions
Is Black Diamond or Onyx more durable?
Black Diamond is harder (Mohs 10 vs 6.75), so it resists scratches better.
Which is cheaper, Black Diamond or Onyx?
Black Diamond runs about $200 to $3,000 per carat and Onyx about $3 to $40 per carat, so Onyx is usually the more affordable choice.
Which should I choose?
Pick Black Diamond if you want black tones and Onyx if you prefer black. Match the stone hardness to how you will wear it and let budget break the tie.