Yes, it is very common. It is mainly composed of weathered diatom skeletons (diatomaceous earth that has been microscopically crushed and tumbled throughout geological time). It has a small percentage of clay in it, too, going by the 9% alumina content. The way the materials (all of them) are prepared, by both the mine and the operator, makes a difference, too… granulated white RVM (regular volatile material) opaline silica and same granulated LVM (low volatile material) anaerobic low temperature calcined montmorillonite (gray not red, high temp aerobic LVM bentonite) are comparable, but the white opaline silica works best. Both should be oven dried in layers no more than 2 or 3 inches thick at over 300°F, preferably under vacuum. Just make sure to use a scroll or diaphragm pump (LOTS of water comes out) and filter the line of dust by wrapping the pans in 100% cotton pillowcases if you use vacuum!