Obsidian vs Onyx
Both popular gemstones that share a similar color palette, Obsidian and Onyx are frequently compared by gemstone enthusiasts. Obsidian scores 5.0 on the Mohs hardness scale while Onyx scores 6.5. Price-wise, Obsidian is budget-friendly and Onyx is moderately priced.
| Property | Obsidian | Onyx |
|---|---|---|
| Category | Semi-Precious Gems | Semi-Precious Gems |
| Primary Color | black | black |
| Mohs Hardness | 5.0–5.5 | 6.5–7.0 |
| Specific Gravity | 2.35 | 2.55 |
| Refractive Index | 1.45 | 1.53 |
| Crystal System | Amorphous | Trigonal |
| Luster | Vitreous | — |
| Chemical Formula | — | — |
| Price Tier | Budget (< $50/ct) | Moderate ($50-500/ct) |
| Daily Wear | لا | لا |
Key Differences
- ◆ {'gem_a': '5.0', 'gem_b': '6.5', 'property': 'Hardness (Mohs)'}
- ◆ {'gem_a': 'Amorphous', 'gem_b': 'Trigonal', 'property': 'Crystal System'}
- ◆ {'gem_a': '2.35', 'gem_b': '2.55', 'property': 'Specific Gravity'}
- ◆ {'gem_a': '1.45', 'gem_b': '1.53', 'property': 'Refractive Index'}
- ◆ {'gem_a': 'Vitreous', 'gem_b': 'N/A', 'property': 'Luster'}
- ◆ {'gem_a': 'budget', 'gem_b': 'moderate', 'property': 'Price Range'}
- ◆ {'gem_a': 'No', 'gem_b': 'No', 'property': 'Daily Wear'}
When to choose Obsidian
Choose Obsidian when you want a more budget-friendly price point. It's ideal for collector specimens and carefully worn jewelry.
When to choose Onyx
Choose Onyx when you want superior hardness and scratch resistance, higher brilliance and light performance, and premium quality and rarity. It's ideal for occasional wear pieces and pendants.
Frequently Asked Questions
Which is harder, Obsidian or Onyx?
Onyx is harder at 6.5-7.0 on the Mohs scale, compared to Obsidian at 5.0-5.5. This makes Onyx more resistant to scratching. Onyx requires more careful handling and is not ideal for daily wear, while obsidian requires more careful handling and is not ideal for daily wear.
Is Obsidian more expensive than Onyx?
No, Obsidian is generally less expensive. Obsidian is classified as budget-friendly (under $50/ct) at budget-friendly (under $50/ct), while Onyx is moderately priced ($50-500/ct) at moderately priced ($50-500/ct).
Should I choose Obsidian or Onyx for an engagement ring?
Neither Obsidian nor Onyx is ideal for an engagement ring worn daily. Onyx (6.5-7.0 Mohs) is the more durable of the two, while Obsidian (5.0-5.5 Mohs) is softer. If you choose either, consider a protective setting like a bezel.
How can I tell Obsidian and Onyx apart?
There are several visual cues: both appear black, but often in different saturations; Onyx (RI 1.53-1.543) shows more brilliance than Obsidian (RI 1.45-1.55); they have different crystal systems — Obsidian is Amorphous and Onyx is Trigonal. A gemologist can confirm identification using refractive index testing.
Why do Obsidian and Onyx look similar?
Obsidian and Onyx look similar because both gems display black hues.