Welcome to the forum.
The wheels are I'm assuming carburundum and will have little to none precious metal content and I would suggest adding them to the floor sweeps just in case there is some value. The actual lemel/ dust will be a mix and as advised incineration, not melting, would be a good start to remove the oils,plastics etc. The next step should be to transfer to a beaker on a hot plate, add distilled water to cover and then add nitric acid slowly, this will dissolve any silver in the alloys and many base metals, the silver can be cemented out with copper later. The remaining powder should be filtered and rinsed with distilled water to remove any silver nitrate and then transferred back into your beaker. The dust in my experience will yield around 70% by karat of the incoming weight in gold so calculate how much acids are needed to dissolve it,add say 10% more of the hydrochloric acid, then pour the hydrochloric into the beaker onto your powder and then slowly add the nitric in small increments, only adding more when all reaction ceases, I would advise regular stirring to make sure the acids reach all the gold in the fine powders and to avoid hot spots. Once all reaction has ceased allow the solution to cool, add cold water and then filter again rinsing to remove all the pregnant solution, it can then be precipitated with the reactant of your choice.
All the acid processes will need to be done under a fume hood or with very good ventilation forcing the fumes away from you, they are very dangerous, and all the usual safety equipment will be needed.
Under no circumstances try to melt this material, it's not going to happen unless you really know what your doing and which mix of fluxes to use, even then I find I get more values by the acid processing.
Good luck and read up well on all the processes before trying this and have the right safety in place.
