Testing Diamonds, Moissanite and Simulants at Home
When testing a clear gemstone, you’re typically dealing with one of four possibilities:
- Natural diamond
- Lab-grown diamond (chemically and physically identical to natural)
- Moissanite, a distinct gemstone valued for its exceptional fire and brilliance
- Cubic zirconia or similar simulants, lower-cost imitations that mimic the look of diamond
Lab-grown diamonds are identical to natural diamonds in composition and properties, so at-home testing cannot distinguish those two. What you can do is separate diamond and moissanite from cubic zirconia, and distinguish diamond from moissanite using the right tools.
Note: All of the tools mentioned below, such as diamond testers, loupes, UV lights, magnets, and acid kits, are widely available online from major retailers like Amazon. Higher quality tools generally give more accurate and consistent results.
1. Dual Thermal and Electrical Conductivity Tester
A thermal conductivity tester (diamond tester pen) is the fastest way to check if a stone is diamond. Diamonds conduct heat extremely well, which sets them apart from cubic zirconia and glass.
However, moissanite conducts heat similarly to diamond, so cheaper single-mode testers often misidentify it as diamond. A dual thermal and electrical conductivity tester gives you accurate results:
- Natural and lab-grown diamonds register as diamond.
- Moissanite shows a distinct reading due to its electrical conductivity.
- Cubic zirconia and other simulants show no conductivity at all.
2. Loupe Inspection, Facet Edges and Double Refraction
A 10× jeweller’s loupe can reveal structural differences:
- Diamonds have razor-sharp facet edges and crisp facet junctions.
- Moissanite shows double refraction, look through the crown straight down and you’ll often see doubled facet lines due to its crystal structure.
- Cubic zirconia typically has slightly rounded facet edges and lacks the precision of either diamond or moissanite.
3. UV Fluorescence (Supporting Clue)
Around one-third of natural diamonds fluoresce blue under UV light. This is not definitive but can support your other observations:
- Diamonds may show blue fluorescence.
- Moissanite typically shows little or different fluorescence.
- Cubic zirconia usually does not fluoresce at all.
Testing Gold at Home
Gold testing focuses on separating solid gold from plated or imitation metals. These are the practical methods that work.
1. Magnet Test
Gold isn’t magnetic. A strong neodymium magnet can quickly eliminate non-gold items:
- A firm pull means it’s not gold.
- A weak pull can indicate gold-plated over a magnetic base.
This is a fast first pass, not a conclusive test.
2. Acid Testing Kit
A gold acid testing kit provides a reliable at-home way to determine karat purity. Lightly scratch (in a hidden area!) the jewellery on the testing stone and apply the appropriate acid:
- If the mark remains under the 10K solution, it’s at least 10K.
- Repeat with higher karat acids to estimate purity.
- Always test in an inconspicuous area.
3. Electronic Gold Tester (Optional)
For frequent testing, an electronic gold tester measures electrical conductivity to determine karat without acids. These are more expensive but very accurate.
When Home Testing Isn’t Enough
- Diamond origin: to offically distinguishing natural from lab-grown requires advanced spectroscopy equipment.
- Accurate valuation: if you’re selling or insuring the piece, get a certified appraisal.
- Hallmarks: helpful but not proof, counterfeit hallmarks are common.
With the right tools, you can confidently separate diamonds, moissanite, cubic zirconia, and gold from imitations at home. A dual diamond tester and a basic gold acid kit cover most everyday scenarios.
Moissanite stands on its own as a premium gemstone, not as a substitute. Lab-grown diamonds are indistinguishable from natural diamonds without professional equipment. For anything beyond the scope of home testing, a qualified gemologist remains the final authority.
Thanks for reading!
Jared & Brie
