black Silicon Carbide grit /powder for polishing

Yes, you can if you want, but we bet that you will change your mind after the first batch of rocks. Here are the advantages of using rock tumbler grit (more formally known as "silicon carbide grit"...

1) Silicon carbide grit is very hard. It is much harder than the rocks that most people tumble. On the Mohs Hardness scale silicon carbide has a hardness of 9 to 9.5 while commonly-tumbled rocks such as jasper, agate, quartz and petrified wood have a Mohs Hardness of about 7. This means that silicon carbide grit can easily abrade the rocks that most people tumble. However, most beach, river, and wind-blown sands are composed of quartz, which has the same hardness as the rocks that most people tumble. Since it has an equal hardness it will be ineffective at abrading them in the tumbler barrel.

2) Quality silicon carbide grit usually occurs in angular particles. That means they have sharp points and edges that facilitate abrasion on the rocks while tumbling occurs. However, most beach, river, and wind-blown sands have rounded particles, which makes them ineffective at abrading the rocks that you are hoping that they will grind.

3) Rock tumbler grit can easily be purchased in sizes that are perfect for rock tumbling. To duplicate the coarse, medium and fine grits used in rock tumbling you would have to purchase a set of sieves, find sand of various particle sizes and separate it into the grit sizes needed for rock tumbling. We are willing to bet that you will burn more gasoline and time chasing these special particle sizes of sand than you would spend buying some good grit. It isn't that expensive.

In summary, you can use sand instead of rock tumbler grit. But, if you do that, the sand may not be effective at cutting the rocks because it has the same hardness as the rocks and it usually occurs in rounded grains. You will probably waste a lot of time and electricity trying to save money using sand instead of rock tumbler grit. We have an article titled "Can I Use Sand Instead of Grit?" that explains this in much more detail.