Here are our recommendations for untreated gem varieties: These can be bought with confidence, knowing that they are completely natural gems. There are a number of gemstone varieties that combine good gemstone characteristics - hardness, durability, brilliance and clarity - with outstanding color, yet are never treated. However, there is no need to pay a fortune for very rare untreated sapphires or rubies. Some of those ancient techniques were undoubtedly deceptive, but nowadays, gem treatments are just a way for the industry to meet the global demand for gemstones in the face of very limited supply.ĭespite the proliferation of gem treatments, there are still many choices for buyers who insist on an untreated gem.
Pliny's Natural History, the compendium of knowledge from ancient Rome written in the first century A.D., discusses a range of techniques for altering gems, including heating, oiling, dyeing and the use of foil backings and coatings.
