Quartz -
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Quartz -

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Questions and Answers

What is 'tourmalinated quartz' characterized by?

  • dark-hued tourmaline inclusions (correct)
  • orange-red pleochroic flashes
  • small inclusions of mica
  • reddish or golden rutile crystals

    • What is the color of rock crystal?

  • light yellowish brown or orange-brown
  • medium-dark to moderately strong orange
  • colorless and transparent (correct)
  • vivid to strong purple or violetish purple

    • What is the chemical composition of all quartz varieties?

  • oxygen and aluminum
  • silicon and oxygen with aluminum impurities
  • silicon and oxygen (correct)
  • silicon and oxygen with iron impurities

    • What is the trace element responsible for the color of Citrine?

    <p>iron</p> Signup and view all the answers

    What type of rocks can quartz form in?

    <p>pegmatite, volcanic, and sedimentary rocks</p> Signup and view all the answers

    What is the characteristic of Smoky Quartz?

    <p>it has a light yellowish brown or orange-brown color</p> Signup and view all the answers

    What is the characteristic of Amethyst?

    <p>it has a vivid to strong purple or violetish purple color</p> Signup and view all the answers

    What is the characteristic of Rose Quartz?

    <p>it has a very light pink to medium-dark pink color</p> Signup and view all the answers

    What is the Mohs scale of Quartz?

    <p>7</p> Signup and view all the answers

    Which of the following is a type of Quartz?

    <p>Chalcedony</p> Signup and view all the answers

    What is the color range of Amethyst?

    <p>Strongly saturated violetish purple to reddish purple</p> Signup and view all the answers

    What is the effect of brownish or bronze-colored tints on the price of Amethyst?

    <p>It decreases the price</p> Signup and view all the answers

    What is Lemon Quartz?

    <p>Irradiated and then heated Smoky Quartz</p> Signup and view all the answers

    What is the color range of Citrine?

    <p>Transparent, yellow to brownish orange</p> Signup and view all the answers

    What is the effect of medium-dark to dark reddish purple or purple color on the price of Amethyst?

    <p>It increases the price</p> Signup and view all the answers

    What is Chalcedony a type of?

    <p>Quartz</p> Signup and view all the answers

    What is the crystal system of Quartz and Chalcedony?

    <p>Trigonal</p> Signup and view all the answers

    What is the characteristic of Rose Quartz?

    <p>Tends to internal fractures giving a cloudy translucence</p> Signup and view all the answers

    What can cause asterism in Rock Crystal and Smoky Quartz?

    <p>Numerous small inclusions</p> Signup and view all the answers

    What is the common treatment for Amethyst?

    <p>Heat treatment</p> Signup and view all the answers

    What is the result of heat treatment on Amethyst?

    <p>It turns yellow</p> Signup and view all the answers

    What is the characteristic of Citrine?

    <p>Color zoning and inclusions</p> Signup and view all the answers

    What is the characteristic of Smoky Quartz?

    <p>It has phantom effects</p> Signup and view all the answers

    What is the name of the quartz that has eye-visible needle-like mineral inclusions?

    <p>Sagenitic quartz</p> Signup and view all the answers

    Which of the following countries is NOT a source of Rock Quartz?

    <p>China</p> Signup and view all the answers

    What is the primary method of synthetic production for Amethyst?

    <p>Hydrothermal method</p> Signup and view all the answers

    Which of the following is a type of Amethyst grade?

    <p>African</p> Signup and view all the answers

    What is the typical color of Amethyst graded as 'light' or 'C'?

    <p>Grayish pale purple</p> Signup and view all the answers

    Which of the following is NOT a cutting and marketing center for Amethyst?

    <p>South Africa</p> Signup and view all the answers

    What is the primary reason for the production of synthetic Quartz?

    <p>For use in electronics industry</p> Signup and view all the answers

    Which of the following is a type of Quartzite source?

    <p>All of the above</p> Signup and view all the answers

    What is the primary material used to produce synthetic Amethyst via the hydrothermal method?

    <p>Twinned natural seed crystal</p> Signup and view all the answers

    What is the result of heat treating very dark Smoky Quartz?

    <p>It changes to a greenish yellow resembling citrine</p> Signup and view all the answers

    Which type of quartz is often treated with irradiation to intensify its color?

    <p>Rose Quartz</p> Signup and view all the answers

    What is the effect of quench-crackling on Rock Crystal quartz?

    <p>It displays rainbow iridescence</p> Signup and view all the answers

    What is often done to Tiger's Eye quartz to produce a brighter color?

    <p>Dyeing</p> Signup and view all the answers

    What is the common use of Quartzite?

    <p>Dyeing to resemble jade</p> Signup and view all the answers

    What is the characteristic of Amethyst from Zambia?

    <p>It has a deep color and is often too dark</p> Signup and view all the answers

    Which type of quartz is often cut into emerald cuts with a focus on half and half distribution?

    <p>Ametrine</p> Signup and view all the answers

    Where is the Anahí mine, a source of natural Ametrine?

    <p>Bolivia</p> Signup and view all the answers

    Study Notes

    Quartz Varieties

    • Ametrine: a transparent, bicolor variety of quartz containing both amethyst and citrine, with a medium-dark to moderately strong orange and vivid to strong purple or violetish purple color.
    • Smoky Quartz: a light yellowish brown to dark brown variety, with very dark brown Smoky Quartz being called Morion, and the best quality having a deep reddish brown color with orange-red pleochroic flashes.
    • Rose Quartz: a very light pink to medium-dark pink variety, with the finest quality being highly transparent.
    • Rock Crystal: a colorless, transparent quartz variety, with "tourmalinated quartz" having dark-hued tourmaline inclusions, and "rutilated quartz" or Venus hair stone having hair-thin reddish or golden rutile crystals.
    • Cat's Eye Quartz: a semitransparent to translucent brownish yellow, brownish green, or greenish yellow variety.
    • Tiger's Eye Quartz: a semitranslucent to opaque gem with a pattern of lustrous yellow and brown bands that reverse color, with "zebra tiger's-eye" being a variegated grayish blue and brown variety, and "hawk's-eye" or falcon's-eye being a grayish blue color.

    Chemical Composition

    • All quartz varieties have a base of silicon and oxygen.
    • Amethyst: trace element is iron.
    • Citrine: trace elements are iron.
    • Smoky Quartz: natural radiation involves aluminum impurities.

    Forming Source

    • Quartz varieties are formed in pegmatite, volcanic, and sedimentary rocks.

    Crystal Structure

    • All quartz varieties fall under the trigonal crystal system.
    • Quartz and Chalcedony have different sizes of crystals, including large single or twinned crystals, microcrystalline aggregates of small crystals, and cryptocrystalline aggregates of tiny microscopic crystals.

    Phenomena

    • Chatoyant: a phenomenon where the gemstone appears to have a narrow, bright band of light.
    • Aventurescence: a phenomenon where the gemstone appears to have glittering, metallic inclusions.
    • Rose Quartz: numerous small inclusions can create asterism.
    • Rock Crystal and Smoky Quartz: can have "phantom effects" with a v-shaped color band visible with the unaided eye.

    Clarity Characteristics

    • Amethyst: color zoning and inclusions.
    • Citrine: color zoning and inclusions.
    • Rose Quartz: tends to internal fractures, giving a cloudy translucence.
    • Rock Crystal: eye inclusions, with "Sagenitic quartz" or sagenite having eye-visible needle-like mineral inclusions.

    Treatments

    • Amethyst: heat treatment is most common to lighten dark stones.
    • Citrine: natural citrine is rare, most on the market is the result of heat treatment.
    • Ametrine: heat treatment or a combination of heat treatment and irradiation.

    quartz and Chalcedony

    • Quartz is a larger crystal structure.
    • Chalcedony is a Quartz species with a smaller crystal structure.

    Largest Consumers

    • Rock Crystal: China and the USA.

    Mohs Scale

    • Quartz has a hardness of 7 on the Mohs scale.

    Variety/Species/Group

    • Quartz is a larger crystal structure.
    • Chalcedony is a Quartz species with a smaller crystal structure.

    Color/Hue Range/Value

    • Amethyst: hues range from strongly saturated violetish purple to reddish purple.
    • Citrine: transparent, yellow to brownish orange variety of quartz.
    • Smoky Quartz: light yellowish brown to dark brown variety.
    • Rose Quartz: very light pink to medium-dark pink variety.
    • Rock Crystal: colorless, transparent quartz variety.
    • Tiger's Eye Quartz: semitranslucent to opaque gem with a pattern of lustrous yellow and brown bands.

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