Simulated gemstones synthesized in a lab to imitate natural stones. However, not all simulants are synthetic. Synthetic gems are man-made material with essentially the same chemical composition, crystal structure and optical and physical properties as the natural gem material.
Fine silver, for example 99.9% pure silver, is relatively soft, so silver is usually alloyed with copper to increase its hardness and strength. Sterling silver is prone to tarnishing, and metals other than copper can be used in alloys to reduce tarnishing, as well as casting porosity and firescale.
A number of large or extraordinary diamonds have gained fame, both as exquisite examples of the beautiful nature of diamonds and because of the famous people who wore, bought, and sold them. Among the most well known diamonds is the Hope diamond.