The images below show the heavy liquids technique we use to separate zircon. We use bromoform which has a density of 2.85 g/cm3. Minerals heavier will sink (like zircon!), lighter stuff will float (like quartz!). After heavy liquids, we are hopefully just left with a bunch of zircon, which you can see in the middle picture. Upon closer inspection under the microscope, you can see that there are pieces of non-zircon material. In the third photo you can see individual grains, which range in length. Some pieces are even dust-sized! The zircon pictured below are from a bulk rock sample (about a gallon) that was collected in the Black Rock Desert. This is actually quite a lot of zircon, another sample that was processed didn’t have nearly as much.
This link will take you to a video of heavy liquids in action!