This page contains a gemstone guide to common abrasives used near gemstones; their usage, hardness rate and effects compiled by Tom Weishaa CMBJ.
Abrasive
Silicon Carbide
- Usage – A common abrasive found in most mizzy wheels, cut-off discs and some aggressive rubber wheels. Silicon carbide usually appears as small silver flecks of metal.
- Hardness – 9.5
- Effect – Will damage all gemstones. Even diamond under some circumstances.
Aluminum Oxide
- Usage – Common abrasive found in many types of medium cut rubber wheels
- Hardness – 9
- Effect – Will abrade most gemstones
Corundum
- Usage – Common abrasive found in many types of medium cut rubber wheels.
- Hardness – 9
- Effect – Will abrade most gemstones
Ceramic
- Usage – This abrasive is becoming more popular as a fine cut. Often suspended in silicone wheels.
- Hardness – 7.5
- Effect – Will abrade many softer gemstones
Steel Tools
- Usage – Hardened steel tools; files, burs and burnishers are often wrongly used to shape prongs or bezels directly on gemstones.
- Hardness – 7.5
- Effect – This practice can harm all soft stones and can abrade facets junctions on gemstone harder than the steel.
Silicone
- Usage – Once used as a binder, silicone is now becoming popular as a fine-finishing wheel.
- Hardness – 7
- Effect – Will wear down some soft gemstones
Pumice
- Usage – Effective when used to remove tool marks from prongs in close proximity to gemstones.
- Hardness – 5
- Effect – Can be used directly on most gemstones
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