Turquoise had been popular in many ancient civilizations such as those in Egypt, Persia, China, and the Americas. Europeans got to know about this then "exotic gem from the east" from the Turkish traders (hence the name) that brought them over from Persia.
Turquoise art, Turquoise gems are still widely sought after today because of their unique combination of color and opacity. It is one of the most popular non-transparent gems around. Turquoise looks good on any setting, metal or otherwise. Cabochon, beads, and other fancy shapes are the most common cuts instead of facets. Exceptionally large nuggets and blocks of turquoise can also be sculptured into various types of wearable works of art or non-wearable decorative items. Turquoise characterTurquoise has hues that vary from blue to green or yellow-green, with all the possible combinations in between. It has a sheen or luster that is typically similar to that of wax or rough glass; and it is one of the softest of gemstones, having a Mohs scale hardness rating of only 6, which is one rank below that of the common mineral quartz. Turquoise specimens are also highly porous because they are made up of millions of individual interlocking cryptocrystalline turquoise crystals. Brown, black, or gray-brown flecks or veins made up of other minerals such as pyrite are often found embedded in turquoise....Turquoise care, Because of its softness, turquoise is usually treated either with wax or resin. Wax treatment of turquoise has been practiced since ancient times and it does not add or detract from the value of the gem since most turquoise has a natural waxy luster. Bare turquoise pieces must be periodically waxed (with beeswax or paraffin) to protect them from light, heat, perfumes, moisture, sweat, and so on. Resin treatment imparts greater durability to each individual specimen compared to waxing. Resin treatments are sometimes preceded by color-enhancing treatments, but the highest quality turquoise gems do not need to be color enhanced and as such are only treated with colorless protective resins. Blue topaz contrast to the opaque turquoise, blue topaz--the substitute modern birthstone for December--is exceedingly clear and transparent, particularly the highest-quality gem specimens. Topaz typically has the luster of diamond or glass, which also contrasts with the waxy or rough glass luster of turquoise. Naturally blue topaz is quite rare and usually has a pale blue or sky-blue tone. The purer the blue hue (little or no extraneous browns or grays), the higher the values these gems acquire. Topaz treatments Some blue topazes get their color from radiation and heat treatments. These treatments are acceptable as long as they are declared. Usually the darker the resultant tone (e.g., London blue), the more expensive the specimen. However, note that irradiation and heat treatments may make topaz gems more brittle thereby making them more sensitive to mechanical stress and wear. Reputable labs that treat topazes indicate the appropriate enhancement codes and gem re-fashioning warnings on their product literature. For additional information on topazes, please see our previous article on this Mays birthstone.