Gemstone Guide

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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