The Glory of Blue
Blue Agate is a layered form of chalcedony quartz. It is known to occur in a wide variety of colors and interesting patterns, including many shades of light to dark blue. Some popular trade names used for blue agate include blue lace agate, Mohave blue agate and blue banded agate. Many agates today may have been dyed, but unlike many other gem types, the dyeing of agate does not normally affect its value. However, any such treatment should always be disclosed by gemstone traders. Agate has excellent hardness and durability, making it one of the most versatile blue gemstones today.
Blue Aquamarine is a member of the beryl family and is colored by traces of iron. Its color can range from blue to bluish-green and is typically very subtle, especially when compared to more vivid and intensely colored blue gemstones such as blue topaz. Aquamarine is one of the few naturally blue untreated gemstones (although some darker stones may be heated) and it has excellent hardness and durability. It is also known to occur with rare cat’s eye chatoyancy. Aquamarine is also the official modern March birthstone.
Blue Apatite is composed of calcium phosphate, the same material that makes up our teeth and bones. Although it is a very common mineral, gem-quality materials are extremely rare. Apatite is the defining mineral for 5 on the Mohs scale and it is known to occur in a wide variety of colors including a ‘Paraiba’-like blue-green. Apatite is normally untreated, but one variety known as ‘moroxite’, is routinely heated to enhance its color. Some rare apatite gemstones may exhibit cat’s eye chatoyancy, known in the trade as cat’s eye apatite.
Blue Azurite is a rare gem-quality variety of copper ore. There are two basic copper carbonate minerals – azurite and malachite. Of the two, azurite is much rarer. Azurite has a very distinctive and vivid blue color often described as, ‘azure blue’, hence its name. Azure blue refers to the unique deep lapis-like color seen in fine quality azurite. Azurite may also be found mixed with malachite, forming attractive blue-green gemstones. Azurite druzy is also very popular for jewelry, and it is much more durable for wearing owed to the hardness of its matrix rock.
Blue Benitoite is a rare mineral first discovered in California by James Couch in 1907. It is a fine blue barium titanium silicate. It is one of the rarest gemstones available today. Benitoite has a higher dispersion rating than diamond and is known to display impressive brilliance and fire. Though the mineral benitoite has been found in various locations around the world, gem-quality and facetable material has only been found in San Benito, California. Benitoite is the official state gemstone for California.
Blue Chalcedony belongs to the quartz group of minerals. Technically, ‘chalcedony’ is the umbrella term for all cryptocrystalline quartz. It can occur in a wide range of different colors, sizes and patterns. In the gemstone trade however, the term ‘chalcedony’ is typically used only to refer to ‘chalcedony in the narrow sense’ or ‘actual chalcedony’, which is the solid colored, translucent light-white to bluish gemstone. It’s been recently discovered that chalcedony quartz is actually a combination of quartz and a polymorph known as moganite. Chalcedony takes an excellent polish and high quality materials can exhibit a glowing attractive luster.
Blue Chrysocolla is a gem-quality hydrous copper silicate. It appears similar to both azurite and malachite. Although chrysocolla is most famous for its vivid blue to cyan green color, it can also be found in a wide variety of unusual and unique combinations of blue and green. Chrysocolla is colored by copper and is often confused with turquoise because of its similar color and appearance. Identifying chrysocolla by composition can be extremely difficult since it lacks a definitive chemical composition. Any blue to green copper-bearing silicate that cannot be specifically identified as something else otherwise, can essentially, be identified as chrysocolla. Most gem labs will not confidently issue identification reports for chrysocolla for these reasons mentioned.
Blue Diamond is the hardest known natural material on earth, rating 10 on the Mohs scale of mineral hardness. Its name comes from the Greek word ‘adamas’, meaning invincible. Diamond is composed of pure carbon, the same material that makes up graphite, a very common material used in the production of pencil lead and various other industries. Blue diamond is typically irradiated to obtain its color, though some very rare stones may be completely natural and untreated. Most blue diamond will exhibit a secondary greenish hue. Blue diamond is prized for its rarity, exceptional hardness, high refractive index and high dispersion rating – the ability to split white light into its component colors.
Blue Sapphire is the best-known blue gemstone (though it also occurs in many other colors). Sapphire’s blue color can range from light-blue to deep-blue. Since sapphire is a gem-quality form of corundum, it is incredibly hard and durable, with a hardness of 9 on the Mohs scale. It is also considered to be one of the most precious of all gems available today. Some blue sapphires are known to exhibit phenomenal characteristics such as asterism (star) or color shift abilities. Today, blue sapphire from Sri Lanka (Ceylon) is considered most desirable, but previously, finds from Kashmir and Mogok, Burma, were known to be the finest quality. Blue sapphire from Cambodia (Pailin) was also known to be of distinctive purity. Many even consider Pailin sapphire to be close in quality to Kashmir, Burmese and Sri Lankan (Ceylonese) sapphire. Sapphire can also be found with phenomenal traits, such as rare color change sapphire, as well as remarkable chatoyant star sapphire. Blue star sapphire is highly sought-after and especially valuable by collectors and jewelers alike. Sapphire is also one of September’s birthstones.