Grinding stone into powder is something you might need to do for all sorts of reasons. The process of assaying ore samples for mineral content usually requires that stone be ground down to a fine powder. Other reasons for grinding it might also include the production of ingredients for chemicals, dyes or building materials. Although most types of stone are very hard in substance, some basic mechanical tools allow them to easily be turned to dust.
Take a desired quantity of stone and break it down into manageable chunks that are no bigger than the size of your fist. If the stone is already this size then you are ready to begin the first part of crushing it fine, but if if your samples are very large, use a sledge hammer to shatter them down into fist-sized pieces or smaller.
Take your pile of fist-sized stone pieces and feed them two or three at a time into a mechanical jaw crusher. This is a device with a large opening on top of it, inside of which are two heavy steel plates which angle downwards towards each other. When the machine is turned on, one of the plates vibrates quickly back and forth against the other fixed plate, pushing the rock downward where the vibrations and tightening space crushes the stone into course sand. Jaw crushers can be rented from most aggregate equipment renters.
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Bag your crushed rock sand and put it through a device known as a vibrating pulveriser. This will crush your sand into fine dust. A vibrating pulveriser is a large metal box inside of which there is a spring supported platform with an air inflated clamp above it. Into this platform you place a thick, lidded steel container which contains your course rock sand and a steel disk or "puck." The box, once activated, vibrates the platform vigorously for a minute or two and the resulting motion causes the steel disk to turn the rock inside the container into dust. Place enough sand into the steel container to fill it half way while it also contains the disk. Then place it inside its platform, close the lid on the grinding mill and press the dual buttons which will inflate the air clamps inside and start the platform vibration process.
Remove the container from the pulveriser once the vibration process has stopped and open it to spill out your now powdered sand. You should be careful when handling the container as often it can be hot from the friction caused by all the vibration. Place the samples of rock powder into plastic bags or containers.
Crushing stone though the jaw crusher is easy work because the machine is capable of pulverizing dozens of pounds of rock per minute. The pulveriser, on the other hand, can only turn a few cupfuls of sand into dust per minute, so this will be slow work if you have a lot of material to convert. Wear eye protection gear, the jaw crusher can often send shards of rock flying into the air from the compression it puts them through. Wear a respirator or mouth and nose protector; rock dust can be very harmful to the lungs if inhaled.