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Specific gravity, also known as relative density, varies depending upon the chemical composition and crystal structure type. Heavy liquids with a known specific gravity are used to test loose gemstones. Specific gravity is measured by comparing the weight of the gem in air with the weight of the gem suspended in water.
Today, depending on the dealer, "Pinchbeck" can mean original Pinchbeck or any gilt metal. [1] Pinchbeck fell out of use in the second half of the 19th century, being replaced by low-carat gold which had been legalised in 1854. [3] Pinchbeck is typically composed of copper and zinc in ratios of 89% copper to 11% zinc; or 93% copper to 7% zinc. [4]
Like ballas diamond, carbonado lacks cleavage planes and its specific gravity varies widely from 2.9 to 3.5. Bort diamonds, found in Brazil, Venezuela, and Guyana, are the most common type of industrial-grade diamond. They are also polycrystalline and often poorly crystallized; they are translucent and cleave easily. [8]
Its specific gravity is high at 5.9–6.1 and its hardness is low at 4.5–5. [2] Aside from pseudo-octahedra, scheelite may be columnar, granular, tabular or massive in habit. Druzes are quite rare and occur almost exclusively at Zinnwald, Czech Republic. Twinning is also commonly observed and crystal faces may be striated.
Britannia metal (also called britannium, Britannia ware, [1] or Vickers White Metal [2]) is a specific type of pewter alloy, favoured for its silvery appearance and smooth surface. The composition by weight is typically about 92–93% tin , 5–6% antimony , and 2% copper .
Jet has a Mohs hardness ranging between 2.5 and 4 and a specific gravity of 1.30 to 1.34. The refractive index of jet is approximately 1.66. The touch of a red-hot needle should cause jet to emit an odour similar to coal. [8] Jet may induce an electric charge like that of amber when rubbed. [7]
Monel alloy 400 has a specific gravity of 8.80, [7] a melting range of 1300–1350 °C, an electrical conductivity of approximately 34% IACS, and (in the annealed state) a hardness of 65 Rockwell B. [8] Monel alloy 400 is notable for its toughness, which is maintained over a considerable range of temperatures.
A United States Navy Aviation boatswain's mate tests the specific gravity of JP-5 fuel. Relative density, also called specific gravity, [1] [2] is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.