Mohs scale hardness: 5-5.5
Lapis Lazuli (also called lapis) is a beautiful blue microcrystalline gemstone composed primarily of lazurite (25%-40%), other minerals include alumunium, sodium, oxygen, silicon, sulfur, chloride and pyrite. Because lapis lazuli is composed of so many minerals, it is called a rock rather than a mineral. Most lapis lazuli are also contains sodalite (blue), calcite (white), and pyrite (metallic yellow). Other possible constituents are augite, diopside, mica, enstatite, hornblende, hauynite and nosean. Some also contain trace amount of the sulfur rich lollingite variety geyerite. Patches of pyrite in the gems are an important help in identifying the stone as genuine and do not detract from its value. Lapis lazuli occurs usually in crystalline marble as a result of contact metamorphism.
Lapis Lazuli Color
The color of top quality stones is evenly distributed, but in general the color is spotted. Other than lazurite, the composition of the minerals influence the color as well. Too much of the same mineral gives a dull, greenish tint. Well-distributed fine pyrite highlights the color of the gem with a brassy gold shimmer. Most collectors and admirers of fine lapis lazuli agree that the less calcite the rock contained, the better it will be. Calcite can be seen as patches or streaks within the darker blue, it can also predominate in the mix giving the color of the rock an overall lighter blue shade. The blue color of the gem comes from the sulphur content and may range from pure ultramarine to a lighter blue. The finest color is intense blue, and lightly dusted with small flecks of golden pyrite.
Lapis Lazuli Gemstone Treatments
People who carve lapis lazuli have to use protective gear in order to avoid silica deposits in the lungs. An experienced cutter can even tell how intense the color of the stone just from smelling the odour. Lapis Lazuli is often dyed or light heating to improve its colour and the stone has been imitated by dyed jasper and by paste with inclusions of copper. A lapis lazuli can easily be repolished at any time even if the gem has been worn too much and grown matt. Lapis lazuli is often sealed with synthetic resin or colourless wax. This sealing process has the effect of improving the stone's wearing qualities (as long as the substances are not mixed with any colouring agent). An inferior lapis is mostly dyed to improve its color, producing a dark blue with a noticeable grey cast whch may also appear as a milky shade.
The stone should not be exposed to too much sunlight and should always be protected from acidic substances. When you drop a hydrochloric acid on the rock, there will be a reaction that results in a rotten egg smell. Since Lapis Lazuli gemstones are soft, they can be easily chipped or scratched and their protective coating can be dissolved by water. Lapis lazuli is somewhat porous, the gems should be protected from solvents or chemicals. One of the best way to clean lapis lazuli is using warm soapy water
These relatively rare gems are also being associated with royalty. Lapis is mostly made into beads of necklace or carved pendants and has been used for more than 6000 years. The name lapis lazuli is derived from the Latin “lapis” meaning “stone” and from the Persian word “lazhward” meaning “blue rock”. This gemstone was called ultramarinum (means beyond the sea) when first introduced to Europe. Lapis Lazuli can be found in Argentina, Afganistan, Canada, United States, Siberia, Pakistan and Chile.
Fake Lapis Lazuli
Since the gem is so popular, there are number of lapis lazuli imitations like German lapis or Swiss lapis, which is a type of jasper stained blue by tthe action of potassium ferro cyanide and ferrous sulphate. Other common imitations are synthetic sintered spinel which produced in Germany, paste (or glass) with spangles of copper crystall inclusions, sodalite and blue dyed chalcedony. Blue lapis imitations were colored with copper sulfate in ancient Egypt to achieve the special deep blue color.
It is believed lapis lazuli have special properties:
• Believed by Romans as a powerful aphrodisiac.
• To increase courage and develop fearlessness.
• To boost up the wearer’s confidence.
• Healing physical problems originating in the head, such as headaches, sinus ailments and speech problems.
Astrologically, lapis lazuli are associated with the zodiac signs of Sagittarius.
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