October 4, 2018

DIY jaw Crusher

Sometimes with high grade gold specimens, you have to crush your ore to recover it's gold.

Gold is often found associated with the mineral quartz. It is sometimes associated with other minerals as well, including iron and manganese oxides, calcite, pyrite and other sulfides as well. It is not uncommon for prospectors, especially those who operate metal detectors, to find a rich gold bearing specimens of ore. Sometimes the best use of these minerals is to sell them at specimens. There are collectors who will pay top dollar for beautiful mineral specimens that contain significant gold. I have done a full webpage to discuss the best ways of getting top dollar for specimens and selling to collectors. Some specimens however, especially those with a large amount of rock and only a limited amount of gold are best crushed and the gold extracted and sold to refiner (information about selling to refiners can also be found on ). Here is a discussion of the procedures to crush Quartz or other minerals and extract the gold from these rich ores.
For really large chunks of material, it may be necessary to initially break down the large pieces with hammers. Sometimes heavy-duty chisels can also come in handy in this part of the process as one breaks down large chunks into fist sized and smaller pieces that can be more easily handled. The classic old mortar and pestle was the method used by early day miners to crush their ore specimens for testing. You can still buy these things today at most prospecting stores - they are made of cast iron and last a long time and work fairly well. It just takes a lot of elbow grease and work to break up the rock. A slightly different version of mortar and pestle work is a variety called hand stamp crushing. A heavy cylinder of iron is welded to a long rod and placed inside a pipe or tube which is just a bit larger than the diameter of the iron cylinder. This iron cylinder is picked up and dropped onto the ore, much in the manner of the old time stamp mills. This method seems to be popular in Australia. A more expensive but certainly faster and easier method is to use a small jaw crusher, such as is used in preparing samples for assaying. I have one of these in my garage and it is pictured at the right. For those thinking about processing larger quantities of ore such as hundreds or even thousands of pounds of rock from mines, there are several manufacturers that sell small portable hammer and impact mills. These mechanized crushing systems can generate some very significant dust, and so when using them is important to consider methods for dust control or elimination.
No matter which crushing system you're using, the process will go far faster, and come out better if you do repeated screenings of the material from time to time. What happens in crushing is that some of the material gets crushed down to the size you want but other pieces don't. The small stuff then often gets in the way of the crushing process as you are working, basically protecting the larger pieces from being crushed and creating more work. To speed things up and make things work properly you need to screen out the stuff that's already been crushed to a small size. So as you are crushing, stop and screen your material, removing any free gold which has already separated from the rock during your crushing that won't go through your screen with your fingers. The coarser rock that won't go through your screen can then be returned to the crusher for further work to break it down, and the fines won't get in the way. If you're screaming of course you need to pick out the screen size you're going to use. It is really not necessary to go to super small screens like 100 mesh. This reduces most of your rock quite literally to powder. The size of screen I use is 18 mesh and I think anything in the range of 16 to 20 mesh is a good size. I would not recommend going with anything larger than 10 mesh or smaller than 30.

Finally, once the rock is fully crushed we get to the part about...