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  2. Gemstone - Wikipedia

    en.wikipedia.org/wiki/Gemstone

    Group of precious and semiprecious stones—both uncut and faceted—including (clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster. A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is ...

  3. List of gemstones by species - Wikipedia

    en.wikipedia.org/wiki/List_of_gemstones_by_species

    Some minerals made into gemstones may display a chatoyancy or cat's eye effect, ... Rock crystal (var.) Shocked quartz (var.) Smoky quartz (var.) Quartzite; R–Z.

  4. List of minerals - Wikipedia

    en.wikipedia.org/wiki/List_of_minerals

    Amethyst crystals – a purple quartz Apophyllite crystals sitting right beside a cluster of peachy bowtie stilbite Aquamarine variety of beryl with tourmaline on orthoclase Arsenopyrite from Hidalgo del Parral, Chihuahua, Mexico Aurichalcite needles spraying out within a protected pocket lined by bladed calcite crystals Austinite from the Ojuela Mine, Mapimí, Durango, Mexico Ametrine ...

  5. List of U.S. state minerals, rocks, stones and gemstones

    en.wikipedia.org/wiki/List_of_U.S._state...

    In 1986, California named benitoite as its state gemstone, a form of the mineral barium titanium silicate that is unique to the Golden State and only found in gem quality in San Benito County. [ 80 ] ^ Colorado is the only state whose geological symbols reflect the national flag's colors: red (rhodochrosite), white (yule marble), and blue ...

  6. Gemology - Wikipedia

    en.wikipedia.org/wiki/Gemology

    Gemstones are basically categorized based on their crystal structure, specific gravity, refractive index, and other optical properties, such as pleochroism. The physical property of "hardness" is defined by the irregular Mohs scale of mineral hardness. Gemologists study these factors while valuing or appraising cut and polished gemstones.

  7. Mineral - Wikipedia

    en.wikipedia.org/wiki/Mineral

    There are about 20 mineral species that qualify as gem minerals, which constitute about 35 of the most common gemstones. Gem minerals are often present in several varieties, and so one mineral can account for several different gemstones; for example, ruby and sapphire are both corundum, Al 2 O 3. [43]