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2. Colored gold - Wikipedia

   en.wikipedia.org/wiki/Colored_gold

   Oxide layers can also be used to obtain blue gold from an alloy of 75% gold, 24.4% iron, and 0.6% nickel; the layer forms on heat treatment in air between 450 and 600 °C. [ 3 ] A rich sapphire blue colored gold of 20–23K can also be obtained by alloying with ruthenium , rhodium , and three other elements and heat-treating at 1800 °C, to ...

3. Gold bar - Wikipedia

   en.wikipedia.org/wiki/Gold_bar

   The standard gold bar held and traded internationally by central banks and bullion dealers is the Good Delivery bar with a 400 ozt (12.4 kg; 27.4 lb) nominal weight. However, its precise gold content is permitted to vary between 350 ozt (10.9 kg; 24.0 lb) and 430 ozt (13.4 kg; 29.5 lb). The minimum purity required is 99.5% gold.

4. Hierarchy of precious substances - Wikipedia

   en.wikipedia.org/wiki/Hierarchy_of_precious...

   The measurement of sales of popular music starts high relative to the wedding anniversary scale, concentrating on gold and platinum (see gold album).Likewise, credit card companies usually have a "gold card" and a "platinum card" (many formerly had a "silver card" then followed by a "gold card", but due to similarity in appearance between silver and platinum these were often discontinued with ...

5. Fineness - Wikipedia

   en.wikipedia.org/wiki/Fineness

   24-carat gold is pure (while 100% purity is very difficult to attain, 24-carat as a designation is permitted in commerce for a minimum of 99.95% purity), 18-carat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-carat gold is 12 parts gold (12 parts another metal), and so forth.

6. Gold-filled jewelry - Wikipedia

   en.wikipedia.org/wiki/Gold-filled_jewelry

   This abbreviation is incompatible with FTC guidelines, which require clear labeling of the gold content and fineness (e.g., 1/20 14K GF). [3] Most high quality gold-filled pieces have the same appearance as high carat gold, and gold-filled items, even with daily wear, can last 10 to 30 years though the layer of gold will eventually wear off ...

7. Material properties of diamond - Wikipedia

   en.wikipedia.org/wiki/Material_properties_of_diamond

   The precise tensile strength of diamond is unknown, though strength up to 60 GPa has been observed, and theoretically it could be as high as 90–225 GPa depending on the sample volume/size, the perfection of diamond lattice and on its orientation: Tensile strength is the highest for the [100] crystal direction (normal to the cubic face ...