Quartz -

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.