A jeweler or a stone cutter (lapidary) will have a way to cut your stone. You'd have to use something harder than sapphire to abrade your stone to see it. Like diamond dust. Most tumblers work with sand (silica) and water. A stone cutter should be able to cut away the matrix and or grind it away to better show the value of your stone and they could give you at least a rudimentary idea of it's worth. Keep in mind the stone will be worth more but they pay the dealer rate which would be lower than market rate. The difference between wholesale and retail might be 300 percent.
A rock polisher might remove some of the matrix material.