Quartz Varieties Visible Spectra (generally 350 - 1100 nm)
The color of some varieties of quartz comes from metal ions substututing
either for silicon in the quartz structure, or in an site normally unoccupied
by ions (interstitial sites). In many of the varieties, the color comes
from small inclusions of other phases.
Images of the spectra of representative varieties
Red jasper; Jasper, red, Crab lake,
Labrador, colored by hematite. This is a reflectance spectrum off a polished
slab. Data Files: Red jasper. The color comes from
small inclusions of hematite, Fe2O3, in the quartz.
Orange-brown jasper; Jasper, orange-brown,
California. This is a reflectance spectrum off a polished slab. Data Files:
Carnelian; Carnelian, unspecified
locality. Data Files: Carnelian.
Rose quartz; Rose quartz, Ramshorn
gulch, Tobacco Root Mountains, Montana. This is a diffuse reflectance spectrum.
Data Files: GRR 1787. The color comes from minute
fibers of an aluminum borosilicate phase contained in the quartz.
Amethyst; Amethyst, Anahí
Mine, Bolivia. Data Files: Amethyst. Amethyst color
develops in iron- containing quartz after exposure to ionizing radiation.
More information is available on our ametrine
Tulare County, California. Data Files: Chrysoprase 17884.
The color of chrysoprase is due to minute inclusions
of a Ni2+ layer silcate in the silica. In the case of the Australian
chrysoprase, the nickel silicate is a member of the talc group which been
identified both as willemseite, (Ni,Mg)3Si4O10(OH)2
and as kerolite, a variety of talc with a randomly stacked structure, in
the series, kerolite - nickel-kerolite.
Smoky quartz: Smoky Quartz, Saline Valley, California.
15.5 mm thick crystal. The color of smoky quartz is due to radiation-induced
color centers. One of the most prominent is centered on aluminum ions that
replace silicon in the tetrahedral site.
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