Aluminium gem gauge that reads diamond carat weight from 0.3 to 4 carats, doubles as an mm sizer, and has a birthstone chart printed on the back.
⭐ At a glance
📏 Measures round stones from 0.3 to 4 carats, with an mm sizing scale alongside
✅ Suitable for diamonds and other round gemstones, loose or mounted
📦 Single gauge tool with birthstone chart on the reverse
✔️ New, unbranded aluminium construction
🔧 What it does & how to use
This gauge lets jewellers, gemologists and hobbyists quickly estimate the carat weight or diameter of a round stone without needing scales, reading the size straight off the graduated scale. It's a handy bench tool for sorting loose stones or checking a mounted gem at a glance, and the birthstone chart on the back gives a quick month-to-gem reference.
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Position the stone: offer the stone up to the graduated scale on the gauge.
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Find the closest match: move along the scale until you find the size that the stone fits against.
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Read the result: take the carat weight or mm figure marked at that point on the scale.
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Cross-check: use the birthstone chart on the reverse if you need to confirm the gem's associated month.
