Best Rock Tumbler Grit

Best rock tumbler grit

What Is The Best Rock Tumbler Grit?


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Polly Plastics Rock Tumbler Tumbling Media

best rock tumbler grit for polishing rocks

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National Geographic Grit Refill for Rock Tumbler

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What Is Rock Tumbler Grit?

Rock tumbler grit is the stuff we use inside the rock tumbler to bring rocks to a nice smooth finish. Rock tumbler grit is a silicon carbide abrasive that is available in different size granules. These varying sized granules are used for shaping, smoothing and polishing rocks in a rock tumbler. Even though there are different kinds of rock tumbler grit, silicon carbide is the preferred grit for rock tumbling.  This is because silicon carbide has three desirable characteristics:

  • Silicon carbide is hard
  • Silicon carbide can be crushed into sharp, angular particles.
  • Silicon carbide is not expensive.

Rock tumbling is done in four different stages and each consists of a different kind of tumbling medium. These stages start with a very coarse rock tumbler grit and gradually work all the way down to a very fine rock tumbler grit.

Because of this change in different kinds of tumbler medium, it is very important to do a thorough cleaning between stages. A thorough cleaning of the barrel is absolutely necessary between each stage.  You want to remove ALL of the grit from the barrel and the rocks before moving on to the next stage.

Kinds of Rock Tumbler Grit

Shaping (60/90 grit)

Shaping grit is the roughest or most coarse of rock tumbler grit. It is used during the first stage of rock tumbling. This is called the shaping stage.  During this stage you are knocking down all of the rough and sharp edges from the rocks by using a very coarse rock tumbler grit.  This stage reshapes your rocks into more round looking stones.



Medium/Fine Grit (120/220 grit)

This stage of the process will remove any scratches, cracks or dimples that might be visible on the rock. To accomplish this, the grit used is not as coarse as the first stage and is  a bit softer.


Pre-Polish (500 grit)

This stage prepares your rocks for the final polish.  This size rock tumbler grit will completely smooth out your rocks, but will not give the high shine that is often time desirable. For that, you must move on to the polishing stage.


Polishing Grit

After your final barrel cleaning, you’re finally ready for the polishing stage!  In this stage you MUST use plastic tumbling pellets to prevent your rocks from hitting against each other and ruining all of the hard work you’ve put in so far. After a week or so in this stage, your rocks should come out looking brilliant and beautiful.


If you’re new to the rock tumbling hobby, or just checking it out, you might find my post, The Best Rock Tumbler For Beginners: Take Your Hobby To The Next Level to be helpful to you on your search.