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The dial is suspended from a cord or chain; the suspension point on the vertical meridian ring can be changed to match the local latitude. The time is read off on the equatorial ring; in the example below, the center bar is twisted until a sunray passes through a small hole and falls on the horizontal equatorial ring.
Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It has also been called "water-sapphire" and "Vikings' Compass" because of its usefulness in determining the direction of the sun on overcast days, the Vikings having used it for this purpose. [ 8 ]
One significant item is a gemstone globe, collected and looted by the Iranian monarchy. For many centuries the Iranian Crown Jewels were kept in the vaults of the Imperial Treasury. However, in the early 20th century, the first Pahlavi Shah transferred ownership of the crown jewels to the state as part of a massive restructuring of the country ...
Gemstone meanings are inspired by everything from royal traditions and chakras to ancient cultures and spiritual thoughts. “The myriad of colors of gemstones alone transmit energy via the ...
the magical or astrological lapidary that sets the relationship between the Signs of the Zodiac and a particular gemstone, and; the Christian lapidary, which describes the symbolism of gems mentioned in the bible, although contemporary readers would have regarded both the first two categories as representing scientific treatments. [4]
Some turquoise contains a matrix of dark brown markings, which provides an interesting contrast to the gemstone's bright blue colour. Some gemstones (like pearls, coral, and amber) are classified as organic, meaning that they are produced by living organisms. Others are inorganic, meaning that they are generally composed of and arise from minerals.
Gemstones are basically categorized based on their crystal structure, specific gravity, refractive index, and other optical properties, such as pleochroism. The physical property of "hardness" is defined by the irregular Mohs scale of mineral hardness. Gemologists study these factors while valuing or appraising cut and polished gemstones.
Peridot is one of the few gemstones that occur in only one color: an olive-green. The intensity and tint of the green, however, depends on the percentage of iron in the crystal structure, so the color of individual peridot gems can vary from yellow, to olive, to brownish-green. In rare cases, peridot may have a medium-dark toned, pure green ...