Fake diamonds can be identified by simple at-home tests like fogging, scratch resistance and sparkle pattern, but the most reliable method is to have the stone assessed by a professional jeweller.
Quick at-home checks:
- Fog test: breathe on the stone – real diamonds disperse fog quickly
- Scratch resistance: diamonds resist scratching; glass and cubic zirconia may show wear
- Sparkle pattern: real diamonds sparkle sharply; simulants show more rainbow fire
Professional testing:
- Diamond testers measure thermal or electrical conductivity
- Gemmologist microscopes reveal facet edges and inclusions
- UV fluorescence can help distinguish some simulants
Note: Lab-grown diamonds share many properties with mined diamonds; only a professional can guarantee authenticity.
Internal links:
- Do you need a diamond certificate? (UK Guide)
- Moissanite vs Diamond: What’s the Difference? (UK Guide)
FAQs:
Is the water test reliable? Water tests aren’t conclusive; density differences are small.
Are lab-grown diamonds fake? No – they have the same physical properties as mined diamonds.
Should I buy a diamond tester? A tester can help, but professional testing is more accurate.
Last updated: January 2026