Coral

Precious coral or pink coral is the common name given to Corallium rubrum and numerous associated species of marine coral. The distinguishing function of precious corals is their durable and very coloured crimson or pink skeleton, that's used for making jewelry. Coral isn't always a mined stone or mineral, but an natural gemstone. It is the hardened, skeleton-formed end result of secretions continuously deposited by means of marine polyps. It looks like a colorful underwater plant, however it's far absolutely a valuable present from the ocean. Coral is discovered in clear at among 15 and one hundred sixty feet. The greater the depth, the lighter the coral's coloration. Coral reefs are determined in almost all of the world's oceans. The largest is the Great Barrier Reef, off the coast of Queensland, Australia. Italian pink coral is in the highest demand In the jewelry industry and is considered the best satisfactory. The best specimens come from Sardinia (Italy) and Tunisia. Coral from Japan and China is taken into consideration barely inferior in high-quality, however it's far greater expensive than Italian red, due to the fact it's miles less abundant. Coral is likewise discovered off the coast of Washington State (U.S.A) and the Aleutian Islands off of Alaska. Unlike maximum other gem stones that are of mineral origin, Coral is organic, fashioned by living organisms. It bureaucracy from branching, antler-like systems constructed from coral polyps in tropical and subtropical ocean waters. When the coral polyps die, the hardened skeleton stays, and this fabric is what is used as a gemstone. Most coral is white, but nature can create coral in several other colors, which include the famous orange to pink forms. This Red Coral, or Precious Coral as it is regularly recognized through, is the most used gemstone shape of Coral. In fact, the shade known as coral is derived from the typical pinkish-orange shade of many pink Coral gemstones. The hard skeleton of red coral branches is naturally matte, but can be polished to a glassy shine. It exhibits a range of warm reddish pink colours from pale pink to deep red; the word coral is also used to name such colours. Owing to its intense and permanent coloration and glossiness, precious coral skeletons have been harvested since antiquity for decorative use. Coral jewellery has been found in ancient Egyptian and prehistoric European burials, and continues to be made to the present day. It was especially popular during the Victorian age. Precious coral has relative density of 3.86 and hardness 3.5 on the Mohs scale. Due to its softness and opacity, coral is usually cut en cabochon, or used to make beads. Coral is usually worn in portions that weigh at the least 3 carats. A ring or pendant can preserve a piece weighing up to twelve carats. Red coral can be set in gold or silver. Chemical Formula Mostly calcium carbonate Colour White, Red, Orange, Pink, Gray, Black Hardness 3 - 4 Crystal System Amorphous Refractive Index 1.48 - 1.65 SG 2.6 - 2.7 Transparency Translucent to opaque Double Refraction -.172 Luster Vitreous, waxy Cleavage None
Sumber http://barokongnetwork.blogspot.com