I have found Quartz crystal; it is covered in red mud and black mud how do I remove this, I tried muriatic acid it either dulls the crystal or does not truly finish cleaning. I have tried soaking in detergent. What is the proper way to clean these????
Quartz crystal straight from the mine is generally dirty. The red and black mud you are referring to is most likely clay and can be cleaned with mild liquid soap and water by soaking and scrubbing with a very soft bristled brush. It is best to make sure the clay is completely dry before soaking. You can tell the clay is dry when it cracks. The soaking and rinsing process may need to be repeated to get the crystals completely clean.
Note: Do not wash your crystals in the sink since clay is likely to plug your drain.
For larger crystals that are hard to clean, a pressure washer may be considered. More difficult residues to remove are gold/brown iron oxide and grey/black manganese oxide. Most rock hounds use an oxalic acid bath to remove this residue. This acid is mild, but can be very dangerous to the skin and lungs if the fumes are inhaled. Oxalic acid is not a product carried by Fire Mountain Gems and Beads, but more product availability, use and safety information may be found online.