Quartz

Abundant and varied, gem quality quartz comes in many forms. Amethyst, smoky quartz, rose quartz, citrine, tiger’s eye, and chalcedony are just some of the members of this large family of stones.

Amethyst
Even though it is by far the most valuable quartz, amethyst is still very affordable thanks to an abundant supply from South America (predominantly Brazil.) Its colors ranges from a strongly saturated violet-purple to reddish-purple. Lower quality amethyst is usually light in saturation with a gray-violet color or with a tint of brown. Visible color zoning will further decrease the value of an amethyst.
While Brazil’s supply is unmatched, perfect for commercial quality amethyst, Zambia is renowned for producing the most beautiful amethyst. Other producers include Madagascar, Tanzania, Mexico, Myanmar, Sri Lanka, and India.

Citrine
Citrine, the top selling yellow-to-orange stone, ranges in color from a pale yellow to a brownish orange. The rarest and most valuable specimens are the ones that show the most intensely saturated red-orange with no traces of brown. Most citrine, because of the scarcity of natural yellow-to-orange stones, are heated amethysts. It is mostly mined in Mexico, Bolivia, Uruguay, and Madagascar while most heated amethyst with a citrine color are produced in Brazil.

Tiger’s Eye
Chatoyancy is displayed in all its glory in the aptly named tiger’s eye- a quartz with trademark brown and yellow bands. The phenomenon is an optical reflectance effect where a band of reflected light moves beneath the surface. Tiger’s eye is usually cut into beads or dyed into other bright colors for fashion jewelry. The main sources of Tiger’s Eye are India, Sri Lanka, Myanmar, and Australia.

Chalcedony
Chalcedony are opaque gems that are usually cut into cabochons or beads. It comes in a variety of colors- green, blue, black, white, purple, orange, brown, and others. Agate is a type of chalcedony that has curved or angular banded markings- some with inclusions that resemble tree branches. Those that come in chrysocolla, a blue-green hue, are the most valuable of all chalcedony and onyx is one of the most well-known.

The biggest sources for chalcedony are Brazil, India, Madagascar, Mexico, and the USA.