Mineralogical Examination

Examples of different mineralogical patina formed by artificially inducing corrosion.

Ammonia vapor can cause beautiful blue crystals to form on the surface of bronze. To the eye these crystals look like azurite, which is often found on ancient corroded bronze. A quick chemical test can tell the difference. Solvents can distinguish between authentic lacquer, made from a tree sap, and modern synthetic lacquer. Simple chemical tests are useful in determining what further action to take when examining artifacts.

Chemical tests, performed on site at TK, are largely based on techniques practiced by mineralogists. They are often performed in conjunction with related tests of physical properties, such as streak color and hardness. A small number of chemicals can be used to detect the presence of numerous elements in a sample. The tests are not quantitative, though the relative proportions of the detected elements may be roughly estimated based on the reactions of a series of tests. With minute samples, impurities may not be detected. In addition to the normal range of chemicals used by mineralogists, solvents may be used to check for the presence of certain adhesives and resins, which are frequently incorporated in applied surface layers on repairs and forgeries. Tests are generally performed on samples of the corrosion crust found on metal objects. Occasionally, a small metal sample will be dissolved for testing. This is generally done when the alloy is unusual or suspicious. In the case of mineral samples, these simple and inexpensive tests generally eliminate the need for XRD analysis. Where the results are remarkable, more advanced testing may proceed.


Chemical analysis of materials, as performed at TK, generally serves to identify corrosion products on metal, and to detect soluble modern adhesives and coatings. The presence of chloride corrosion on metals, especially copper and copper alloys, is considered reason to treat the metal to prevent further potentially destructive corrosion. Chemical tests are usually conducted in conjunction with physical tests, as practiced by mineralogists. The findings may prompt further investigation, using more advanced analytical techniques.