Many gemstones have been treated in various ways to enhance their appearance. For example, sapphires and rubies are routinely heat treated and emerald treated with oils and resins. Some stones may require re-treating or oiling periodically. Enhancement affects market value and all Gardiner Houlgate estimates assume that gemstones may have been enhanced, in any case all lots are sold as seen and purchasers are deemed to have satisfied themselves as to condition and any possibly treatment of stones