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2. Amethyst - Wikipedia

   en.wikipedia.org/wiki/Amethyst

   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+.

3. Tanzanite - Wikipedia

   en.wikipedia.org/wiki/Tanzanite

   Pleochroism. Present, dichroism or trichroism, depending on heat treatment. Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate), caused by small amounts of vanadium. [3] Tanzanite belongs to the epidote mineral group. Tanzanite is only found in Simanjiro District of Manyara Region in ...

4. List of gemstones by species - Wikipedia

   en.wikipedia.org/wiki/List_of_gemstones_by_species

   This is a list of gemstones, organized by species and types. Minerals There ... Herkimer diamond (var.) Milky quartz (var.) Prasiolite (var.) Radiolarite (var.)

5. List of individual gemstones - Wikipedia

   en.wikipedia.org/wiki/List_of_individual_gemstones

   Logan Sapphire. Star of Bombay, given to Mary Pickford by Douglas Fairbanks, Sr. Star of India. Stuart Sapphire. Black Star of Queensland. Star of Adam, with a weight of 1,404.49 carats (280.898 g), it is the largest star sapphire in the world. Queen Marie of Romania Sapphire.

6. Diamond (gemstone) - Wikipedia

   en.wikipedia.org/wiki/Diamond_(gemstone)

   Diamond[a] is a gemstone formed by cutting a raw diamond. Diamonds are one of the best-known and most sought-after gems, and they have been used as decorative items since ancient times. The hardness of diamond and its high dispersion of light —giving the diamond its characteristic "fire"—make it useful for industrial applications and ...

7. Lapis lazuli - Wikipedia

   en.wikipedia.org/wiki/Lapis_Lazuli

   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.