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How to Polish Lake Superior Agate

The Lake Superior agate is found on the shores of the lake in Minnesota, Wisconsin and Michigan, and is Minnesota's state gemstone. Lake Superior agates were formed from lava flows and the formation of the Lake Superior basin early in Earth's history, according to Minnesota Department of Natural Resources. Today, hunting for agates is a popular hobby for residents and vacationers along Lake Superior. Their finds can be polished for use as a gem in jewelry or other decoration.

Things You'll Need

Rock tumbler
Scales
Coarse grit
Medium grit
Pre-polish
Polish
Ivory soap bar

Instructions

- 1
  Select enough agates to fill a rotary rock tumbler barrel at least half full and no more than 3/4 full. Weigh them on a scale, then return them to the tumbler.
- 2
  Add coarse grit to the tumbler. Add approximately 1 tbsp. of grit per pound of rock.
- 3
  Add water to the tumbler so the water is even with the highest layer of agates.
- 4
  Close the tumbler and turn it on. Run the tumbler for one week before checking it.
- 5
  Turn off the tumbler and open it after a week. Remove the agates, which will still be rough, and wash them well. The grit will no longer be coarse, so remove the water and grit mixture and replace it with new water and medium grit. Return the agates to the tumbler.
- 6
  Run the tumbler again for another week.
- 7
  After the second week, wash the agates, remove the water and grit and replace it with water and pre-polish. Tumble in pre-polish for 10 days.
- 8
  Wash the agates, then replace the old water and pre-polish mixture with fresh water and polish. Let the agates tumble for two weeks.
- 9
  Wash the agates again, and replace the polish mixture with a bar of Ivory soap and water. Tumble for several hours, but less than 24 hours. Remove the agates and rinse and dry them thoroughly.

Rocks & Minerals