Padparadscha is a pinkish-orange to orangy-pink colored corundum, with a low to medium saturation and light tone, originally being mined in Sri Lanka, but also found in deposits in Vietnam and Africa. Padparadscha sapphires are very rare, and highly valued for their subtle blend of soft pink and orange hues. The name derives from the Sinhalese word for lotus blossom. Along with rubies they are the only corundums to be given their own name instead of being called a particular colored sapphire.
The rarest of all padparadschas is the totally natural variety, with no beryllium or other treatment, and no heating. To find a stone that is certified by a reputable lab as being completely natural is extremely rare and the stone will be very expensive. High quality, unheated and untreated natural padparadscha sapphires will start off in the range of $5,000 per carat and rise by size, color, tone, cut, and clarity, to $20,000–30,000 per carat.
Purple sapphires are lower in price than blue ones. These stones contain the trace element vanadium and come in a variety of shades. Yellow and green sapphires have traces of iron that gives them their color. Pink sapphires have a trace of the element chromium and the deeper the color pink the higher their monetary value as long as the color is going toward the red of rubies.
Sapphires also occur in shades of orange and brown, and colorless sapphires are sometimes used as diamond substitutes in jewelry. Salmon-colored padparadscha often fetch higher prices than many of even the finest blue sapphires. Recently, sapphires of this color have appeared on the market as a result of a new treatment method called “lattice diffusion”.
Gem quality diamond may be colorless or occur in any hue including the non-spectral hues of gray, brown and black. Diamond is the only gemstone composed of a single element, carbon. The diamond crystal lattice is exceptionally strong and only atoms of nitrogen, boron, hydrogen, phosphorus and maybe beryllium can be introduced into diamond during the growth at significant concentrations. Transition metals Ni and Co, which are commonly used for growth of synthetic diamond by the high-pressure high-temperature techniques, have been detected in diamond as individual atoms, however the maximum concentration is 0.01% for Ni and even much less for Co. Note however, that virtually any element can be introduced in diamond by ion implantation.
In order of rarity, colorless diamond, by far the most common, is followed by blue, green, black, translucent white, pink, violet, orange, purple and red, though yellow and brown are by far the most common colors. “Black,” or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless.