How much quartz is in a 1 ton boulder of quartzite?

Quartzite was originally sandstone composed of quartz grains before undergoing metamorphosis. The result is a m of interlocked quartz crystals, plus whatever mineral(s) originally cemented the quartz grains together to form the original sandstone. Most quartzite is actually about 90% quartz, although some varieties can be up to 99% pure quartz.