This one will be a little bit harder to find. We crush our own down to 1/4" 3/8" also known as cinders.
But you can use the regular 1/2" 3/4" as a base filler and then cover it with a layer of our crushed lava. Call us and we will tell you how much you will need to do this.
Black copper slag is only stocked by us and is used as a filler under our silicone carbide. There are many uses for this product in fires and borders in fireplace and fire pits.