A gem is a precious or semi-precious stone, or a jewel. A silversmith might experiment with adding gems to her rings and necklaces.

The sparkly gem in your grandmother's fancy ring might be a diamond, while your aunt appears to prefer the polished greenish-blue gems called turquoise. If you're trained to identify and put a value on gems, you can call yourself a gemologist. Gem is from the Old French gemme, which has a Latin root, gemma, "precious stone or jewel."

Definitions of gem
  1. noun
    a crystalline rock that can be cut and polished for jewelry
    “he had the gem set in a ring for his wife”
    synonyms: gemstone, stone
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    a highly polished gem that is cut convexly but without facets
    opaque gem
    a gemstone that is opaque
    transparent gem
    a gemstone having the property of transmitting light without serious diffusion
    a rare hard yellow green mineral consisting of beryllium aluminate in crystal form; used as a gemstone
    any of a group of hard glassy minerals (silicates of various metals) used as gemstones and as an abrasive
    a translucent mineral consisting of hydrated silica of variable color; some varieties are used as gemstones
    a transparent purple variety of quartz; used as a gemstone
    a transparent variety of beryl that is blue green in color
    cat's eye
    any of various gems (as chrysoberyl or chalcedony) that reflect light when cut in a rounded shape
    calcedony, chalcedony
    a milky or greyish translucent to transparent quartz
    a brown or yellow-green olivine found in igneous and metamorphic rocks and used as a gemstone
    a green variety of chalcedony valued as a gemstone
    semiprecious yellow quartz resembling topaz
    coral, precious coral, red coral
    the hard stony skeleton of a Mediterranean coral that has a delicate red or pink color and is used for jewelry
    adamant, diamond
    very hard native crystalline carbon valued as a gem
    a green transparent form of beryl; highly valued as a gemstone
    jade, jadestone
    a semiprecious gemstone that takes a high polish; is usually green but sometimes whitish; consists of jadeite or nephrite
    an opaque form of quartz; red or yellow or brown or dark green in color; used for ornamentation or as a gemstone
    a pinkish lilac crystal form of the mineral spodumene that is used as a gemstone
    lapis lazuli, lazuli
    an azure blue semiprecious stone
    a transparent or translucent gemstone with a pearly luster; some specimens are orthoclase feldspar and others are plagioclase feldspar
    a kind of pink beryl used as a gemstone
    a pale green variety of chrysolite; used as a gemstone
    a transparent deep red variety of corundum; used as a gemstone and in lasers
    water sapphire
    a deep blue cordierite often used as a gemstone
    a precious transparent stone of rich blue corundum valued as a gemstone
    a green transparent form of the mineral spodumene used as a gemstone
    aventurine, sunstone
    a translucent quartz spangled with bits of mica or other minerals
    a mineral (fluosilicate of aluminum) that occurs in crystals of various colors and is used as a gemstone
    a mineral that is a complex borosilicate and hydroxide of aluminum containing iron and magnesium and calcium and lithium and sodium; it is usually black but occurs in transparent colored forms that are used as gemstones
    a blue to grey green mineral consisting of copper aluminum phosphate
    type of:
    a solid formed by the solidification of a chemical and having a highly regular atomic structure
  2. noun
    a precious or semiprecious stone incorporated into a piece of jewelry
    synonyms: jewel, precious stone
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    crown jewel
    a precious stone that is a valuable part of a sovereign's regalia
    a gem (usually a diamond) in a setting by itself
    a transparent piece of diamond that has been cut and polished and is valued as a precious gem
    a transparent piece of ruby that has been cut and polished and is valued as a precious gem
    a smooth lustrous round structure inside the shell of a clam or oyster; much valued as a jewel
    a transparent piece of emerald that has been cut and polished and is valued as a precious gem
    a transparent piece of sapphire that has been cut and polished and is valued as a precious gem
    ice, sparkler
    seed pearl
    a small imperfect pearl
    type of:
    jewellery, jewelry
    an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)
  3. noun
    art highly prized for its beauty or perfection
    synonyms: treasure
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    type of:
    art, fine art
    the products of human creativity; works of art collectively
  4. noun
    a person who is as brilliant and precious as a piece of jewelry
    synonyms: jewel
  5. noun
    a sweet quick bread baked in a cup-shaped pan
    synonyms: muffin
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    bran muffin
    muffin containing bran
    corn muffin
    cornbread muffin
    light hollow muffin made of a puff batter (individual Yorkshire pudding) baked in a deep muffin cup
    type of:
    quick bread
    breads made with a leavening agent that permits immediate baking
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