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This mix is a man made material that is a deep shiny green color and has small (roughly 1-3mm) granules. Sold in a 105 gram bag that should finish many pens depending, of course, on how large of a void is filled. This material is very hard and may be difficult to turn. I recommend filling the void below the level to be turned then cap it off with a layer of CA or epoxy which you can turn smooth.

I like to use a small screw driver to transfer the material to the void, fill the void with the material then use thin CA glue to secure. You can use a piece of paper under your pen to catch excess material that may slide off the pen. Before turning, make sure the CA glue has FULLY cured.