Procedure

• A good preparation is a pound of oxalic acid crystals dissolved in about three quarts of distilled water. Soak a specimen for a few days in enough solution to cover it. Applying moderate heat (without boiling) will speed up the process.
  
  

Cleaning Silica

• Oxalic acid effectively cleans iron impurities from silica. Such silica-containing minerals as agate and quartz will receive a fine polished surface when cleansed by an oxalic acid preparation.
  
  

Damage to Minerals

• Oxalic acid will damage some minerals. Oxalic acid preparations will react with minerals containing such elements as iron or manganese and dissolve them. Oxalic acid will also react with calcite and discolor it, according to the New Mexico Bureau of Geology and Mineral Resources.
  
  

Industrial Use

• Sand is the source of silicon dioxide for the manufacture of glass. Oxalic acid can remove iron and other substances from sand so that silicon dioxide is available for glass manufacture in a purer form, according to Minerals Engineering.