The Complete Lapidary Grit Selection Guide: From Rough to Mirror Finish

Introduction

One of the most common questions from beginner lapidary artists is: "Which grit do I start with, and how do I know when to move to the next one?" Choosing the right grit sequence is fundamental to achieving a beautiful, scratch-free finish on your gemstones. This guide walks you through the complete grit progression — from aggressive rough grinding all the way to a breathtaking mirror polish.

Understanding Grit Numbers

Grit numbers refer to the size of the abrasive particles on the wheel or belt. The relationship is simple:

• Lower grit number = Larger particles = More aggressive cutting
• Higher grit number = Smaller particles = Finer, smoother finish

A 60-grit wheel removes material rapidly but leaves deep scratches. A 50,000-grit wheel removes almost no material but produces a mirror-like surface.

The Complete Grit Progression for Lapidary

Stage 1: Rough Grinding (Sintered Metal Bond Wheels)

• 60 Grit — Maximum material removal. Use for trimming rough stones, removing saw marks, and establishing the basic shape. Leaves deep scratches.
• 80 Grit — Still very aggressive. Refines the rough shape established at 60 grit.
• 100–120 Grit — Coarse shaping. Removes 80-grit scratches and further defines the form.

Stage 2: Medium Grinding (Sintered or Hard Flat Wheels)

• 180–220 Grit — Smooths the surface after coarse grinding. Scratches become finer and more uniform.
• 280–360 Grit — Fine grinding. Surface begins to look smoother. Prepares the stone for resin wheel stages.

Stage 3: Fine Grinding (Resin Soft Wheels — Nova or REZ)

• 325 Grit — Transition from metal-bond to resin wheels. Removes medium-grit scratches.
• 600 Grit — Fine grinding. Surface appears smooth to the naked eye but still has micro-scratches visible under magnification.
• 1200 Grit — Pre-polish. Surface looks nearly smooth. A slight sheen may begin to appear on hard stones.

Stage 4: Polishing (Resin Soft Wheels — Nova or REZ)

• 3000 Grit — Early polish. Surface luster begins to develop. Micro-scratches are being removed.
• 8000 Grit — High polish. Excellent finish for most gemstone types. Surface is bright and reflective.
• 14000 Grit — Ultra-fine polish. Recommended for hard stones (Mohs 7+) such as sapphire, topaz, and hard quartz.
• 50000 Grit — Mirror finish. Maximum brilliance. Used for the finest lapidary work and high-value stones.

How to Know When to Move to the Next Grit

This is the most critical skill in lapidary. The rule is simple: never advance to the next grit until all scratches from the current grit are completely removed.

1. Rinse the stone thoroughly under running water.
2. Examine the surface under a 10x loupe or magnifier in good lighting.
3. Look for any scratches that appear deeper or different in direction from the current grinding pattern.
4. If you see deeper scratches, continue on the current grit until they are gone.
5. Only when the surface shows a uniform scratch pattern from the current grit should you advance.

Grit Selection by Stone Hardness

Different stone types require slightly different approaches:

• Soft stones (Mohs 1–5): Malachite, fluorite, calcite — Start at 180–220 grit; skip the most aggressive grits to avoid over-grinding.
• Medium stones (Mohs 5–7): Labradorite, obsidian, turquoise — Standard full grit progression from 100 or 180 grit.
• Hard stones (Mohs 7–9): Quartz, topaz, sapphire, ruby — Full progression from 60 grit; use 14000 and 50000 grit for final polish.

Common Mistakes to Avoid

• Skipping grits — Each grit removes the scratches from the previous one. Skipping creates scratches that are very difficult to remove later.
• Cross-contamination — Always rinse your stone, hands, and work area when changing grits. A single coarse particle on a fine wheel can ruin a polish.
• Rushing — Take your time at each stage. Patience at the grinding stages saves time at the polishing stages.
• Dry grinding — Always use water. Dry grinding generates heat that can crack stones and damage wheels.

Recommended Wheel Combinations

For a complete lapidary setup, we recommend combining:

• Sintered Diamond Wheels (60–360 grit) for rough and medium grinding stages
• Diamond Flat Hard Wheels (180–1200 grit) for precise flat grinding and pre-polish
• Nova or REZ Resin Soft Wheels (325–50000 grit) for fine grinding and all polishing stages

Conclusion

Mastering grit selection is the foundation of great lapidary work. By following a systematic progression from coarse to ultra-fine, inspecting carefully at each stage, and using the right wheel type for each phase, you'll consistently achieve professional-quality results. Explore Hans Lapidary Tools' complete range of sintered, flat, Nova, and REZ diamond wheels to build your perfect grit sequence.