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The normal primary and secondary hues in tanzanite are blue and violet. Untreated tanzanite is a trichroic gemstone, meaning that light that enters this anisotropic crystal gets refracted on different paths, with different colour absorption on each of the three optical axes.
Blood diamonds (also called conflict diamonds, brown diamonds, hot diamonds, or red diamonds) are diamonds mined in a war zone and sold to finance an insurgency, an invading army's war efforts, terrorism, or a warlord 's activity. The term is used to highlight the negative consequences of the diamond trade in certain areas, or to label an ...
Amethyst is a purple variety of quartz (SiO. 2) and owes its violet color to irradiation, impurities of iron (Fe3+. ) and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions. [2][3][4] The irradiation causes the iron Fe3+.
Ametrine, also known as trystine or by its trade name as bolivianite, is a naturally occurring variety of quartz. It is a mixture of amethyst and citrine with zones of purple and yellow or orange. Almost all commercially available ametrine is mined in Bolivia. The colour of the zones visible within ametrine are due to differing oxidation states ...
A mixture of other minerals, often including pyrite. Lapis lazuli (UK: / ˌlæpɪs ˈlæz (j) ʊli, ˈlæʒʊ -, - ˌli /; US: / ˈlæz (j) əli, ˈlæʒə -, - ˌli /), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color.
Jet is a type of lignite, [1] the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid. [2] It is derived from wood that has changed under extreme pressure. The English noun jet derives from the French word for the same material, jaiet (modern French jais), ultimately referring to the ...
The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc, that started in 1947, two years after the end of World War II, and lasted until the fall of the Soviet Union in 1991. The term cold war is used because there was no large-scale ...
The name jadeite is derived (via French: jade and Latin: ilia[6]) from the Spanish phrase "piedra de ijada" which means "stone of the side". The Latin version of the name, lapis nephriticus, is the origin of the term nephrite, which is a different mineral that also shares the common name jade. [7]