Quartz and its colored varieties

Quartz mine in Minas Gerais, Brazil

Iron-containing varieties:

Amethyst

The color of amethyst is the result of radiation damage to Fe3+ in the interstitial site of quartz. The radiation could be due to gamma rays from 40K. Current theory says that the ferric iron is oxidized to Fe4+ by the gamma rays.



Amethyst geodes in basalt near the town of Ametista do Sul, Rio Grande do Sul, Brazil





Amethyst geodes and citrine geodes (heated amethyst ) for sale near Rio de Janerio, Brazil.

Amethyst geode from Rio Grande do Sul, Brazil

Citrine



Synthetic Russian citrine is produced directly by the addition of iron to the growth solutions. It owes its color to Fe3+ clusters in the quartz.

Green quartz

d

d

Specimen provided by SA Kissin.



Synthetic green quartz with Fe2+ in the interstitial site.

Ametrine

Ame

trine

is

amethyst

and

citrine

zones

Smoky quartz

The crystal on the left looked like the one on the right before it was exposed to about 10 Megarads of gamma radiation from 137Cs.



Rose quartz (common, massive rose quartz)

Asterism (star reflection of light) in rose quartz. The reflection comes from the fibers which are partially ordered along the a-axes of the quartz. Photo courtesy of M Scott A scanning electron microscope image of the fibers extracted from rose quartz. The individual fibers are about 0.1 m m wide. The false color in the image is close to the true color of the fibers. SEM photo courtesy of J Goreva, Caltech.

Pink quartz (uncommon, crystalline "rose" quartz)

Al - O2- - P + g -ray ® Al - O- - P + electron



Pink quartz crystals from Minas Gerais, Brazil.

Picture courtesy of S. Pitts A slab of synthetic Russian pink quartz grown with Al and P substitutions and subsequently irradiated with gamma rays to develop the deep rose color.





Specimen courtesy of V Balitsky

Blue quartz

These are inclusions in 'blue quartz' from Madagascar. The ~0.1 mm inclusions are probably in the lazulite-scorzalite series. This blue-grey quartz from Nelson, Virginia, contains micro inclusions of ilmenite. TEM photo courtesy of Ma Chi, Caltech

Chrysoprase

3

4

10

2

Colorless quartz

A large group of colorless quartz crystals from Hot Springs, Arkansas.













Picture courtesy of Jewel Tunnel Imports.

Agate





Fluid Inclusions

This is a smoky quartz crystal from Minas Gerais, Brazil, with a large

fluid inclusion (water) with a large gas bubble above the water.

