Zircon Spectra

The color in zircon (ZrSiO₄) comes from both uranium ions and radiation damage. U⁴⁺ enters the zircon structure because, like Zr⁴⁺, it has a large ionic radius. U⁴⁺ substituting in zircon causes the blue color of heat-treated zircon. Over geologic time, the uranium undergoes radioactive decay and the resulting radiation damage centers cause a range of red-brown and amber colors. Heat treatment removes the radiation damage centers and restores the blue color with which zircon presumably originally crystallized. Green colors are associated with a mixture of the blue color from uranium and red-brown color from radiation damage centers. Highly radiation-damaged zircons are called metamict zircons. Colorless zircons have little uranium.

Zircon Visible Spectra (400 - 1200 nm)

Zircon 1844 ; Brownish-red zircon from Chanthaburi, Thailand, colored by radiation damage. Data files: a (24K) ; c (24K)
Zircon 1486 ; Yellowish-green, partially metamict zircon from Sri Lanka colored by radiation damage. Sharp lines from U⁴⁺ are seen in the spectrum of the 4.4 mm thick sample. Data files: a (24K)
Zircon 1898; Blue zircon from Burma, near the Thailand border. This 2.65 mm thick crystal may have been heat-treated to remove a brownish-red initial color. Data files: a (20K); c (20K)
Zircon; medium green zircon from Burma(?). This 6 mm thick crystal has moderately intense alpha activity. Data files: unpolarized (22K)

A pale brown, a green and a red zircon from Mogok, Myanmar:

Zircon 3106-pale brown plotted as 1.0 mm; Data files: a ; c
Zircon 3106-green plotted as 1.0 mm; Data files: a ; c Most of the spectroscopic features are from U⁴⁺.
Zircon 3106-pale red region plotted as 1.0 mm; Data files: a ; c
Zircon 3106-dark red region plotted as 1.0 mm; Data files: a ; c

Zircon 340, a deep orange-brown metamict zircon from Sri Lanka. The spectrum of this 1.044 mm thick, highly radioactive crystal does not change with polarization direction. When thick , its color is black. Also called zircon 6500 (for 6500 ppm equivalent uranium) and zircon #83057. Extended range spectrum showing OH absorption. Data file: unpolarized

Thorite; Green thorite compared to yellow-green zircon. Both of these show an uranium spectrum.

Link to an extensive collection of references to mostly color and visible spectroscopy of zircons

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last updated:22-Jan-2021