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Chalcedony

Agate

Concentric multicolor banding, highly variable

Banded Multicolor
Optical properties

Optical characteristics

Ref. index
1.53 – 1.543
Birefringence
0.004
Luster
Waxy
Pleochroism
None None.
Fluorescence
Variable; some agates show banded UV fluorescence following the color layers.
Origins

Source localities

Brazil Brazil: Minas Gerais / Paraíba / Bahia
Significant

Major source for beryl, tourmaline, quartz, topaz, chrysoberyl and rare minerals.

30% est. supply
Uruguay Uruguay: Artigas amethyst fields
Significant

Known for amethyst geodes and quartz; produces large agate nodules alongside amethyst.

22% est. supply
India India: Rajasthan / Odisha / Karnataka
Commercial

Historic and modern source for garnet, moonstone, corundum and other gems.

18% est. supply
China China: Xinjiang / Yunnan / Hubei
Commercial

Known for jade, turquoise, quartz and multiple gem deposits.

18% est. supply
United States USA: major gem fields
Commercial

Diverse sources for turquoise, tourmaline, opal, sapphire, topaz, red beryl and rare minerals.

12% est. supply
Treatments

Enhancement & treatment

Color Enhancement Dyeing Dyeing artificially improves color in porous or fractured materials. Durability varies and disclosure is… Heat Heat Treatment, Quartz Heating is common in commercial citrine and other quartz colors. It changes color centers…
Inclusions

Inclusions & features

Zoning Color Zoning Under 10x loupe in immersion: bands or patches of deeper or lighter color arranged… Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small…
Identification

Instruments used

10x Loupe Your most-used instrument, start every examination here UV Lamp, Long Wave and Short Wave Fluorescence exposes treatments, synthetics, and origin High CRI Penlight Tiny concentrated white spot for field checks, inclusions, fire, and fractures