[header] How to polish quartz crystals [title] Use an old toothbrush to wash away clay or dirt. [step] You can do some initial cleaning of your crystals with a toothbrush and water. Make sure you wash the crystals outdoors, as clay and dirt from the crystals can clog a sink. 
[substeps] Scrub the crystal to remove set in clay. You will have to do several rounds of cleaning, allowing the crystals to dry in between rounds.