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How to Polish Labradorite

Updated July 19, 2017

Properly shaped and polished labradorite is one of mineralogy's hidden gems. Despite its simple chemical composition, plagioclase feldspar, labradorite, still shines--literally. Labradorite is one of a few unique minerals that exhibits labradoresence, an optical effect that causes blue and green metallic or pearly shimmers that seem to move as the specimen is turned. This property is best showcased in polished samples of labradorite, which are relatively easy to make yourself, provided you have the time, tools and raw materials.

Break off any adhesions on your sample using a hammer or chisel. Shape the labradorite into the desired shape by chipping at it or rubbing it on concrete. Rough cutting and shaping are also done with a lapidary wheel.

Smooth out the sample with 50-grit sandpaper and gradually work up to finer and finer grit sandpaper, using 150-, then 300- and finally 600-grit. By the last stage, you are no longer shaping the labradorite, but polishing out the scratches from the sandpaper itself.

Use a rock tumbler. Follow your tumbler's specific instructions to put your sample through three grinds--a coarse (3 tbsp of 60 to 90 grit for 7 days), medium (3 tbsp of 110 to 220 grit for 7 days) and fine (3 tbsp of 500 or 600 grit for 7 days)--making sure to wash thoroughly between each cycle.

Polish your sample by rubbing it with a clean, soft cloth (leather or denim work well) and cerium oxide.

Tip

Tin oxide or cerium oxide are the best final polishes for labradorite. Hand polishing with sandpaper is most effective on softer rocks (3 to 4 on the Moh's Hardness Scale); labradorite is a 6 or 6.5, so a rock tumbler can save you some time and elbow grease.

Warning

Always wear safety goggles when chipping at rocks or minerals. Keep your sandpaper and polishing compound damp, since rock dust can be dangerous to breathe. When using a rock tumbler, never dump the used, gritty water down the drain; it will clog your drains.

Things You'll Need

  • Hammer or chisel
  • Sandpaper in varying grits (50, 150, 300, 600)
  • Rock tumbler
  • Caesium oxide
  • Polishing cloth
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About the Author

Jill Brown has been writing and editing technical content since 1998. In 2000, ASM International published a supplement to "Advanced Materials & Processes" called the "Directory of Materials Properties Databases," which Brown compiled, wrote for and edited. Brown earned her Bachelor of Science in geology from Cleveland State University and has taken graduate coursework in environmental engineering.