Thermochromic and
photochromic behaviour
of “chameleon” diamonds
E. Fritsch, L. Massi
Institut des Matériaux Jean Rouxel, Nantes
2 rue de la Houssinière, BP 32229, 44322 Nantes, Cedex 3,
France
G.R. Rossman
Division of Geological and Planetary Sciences 170-25
California Institute of Technology, Pasadena, CA 91125, USA
T. Hainschwang
Gemtechlab, GIA
Switzerland S.A.
2, rue de Chantepoulet, 1201 Geneva, Switzerland
S. Jobic, R. Dessapt
Institut des
Matériaux Jean Rouxel, Nantes
2 rue de la Houssinière, BP 32229, 44322 Nantes, Cedex 3,
France
Abstract
Chameleon diamonds typically change color from greyish-green to yellow
when they are heated or cooled (thermochromic behaviour) or kept in the
dark (photochromic behaviour). Those diamonds are type Ia with A
aggregates largely dominating the nitrogen speciation. They contain
moderate to high amounts of hydrogen, in addition to some isolated
nitrogen and traces of nickel. Their UV Visible spectrum comprises the
continuum typical of type Ib material, the 480 nm band and a broad band
centred around 800 nm. It is mainly modified in the red part of the
visible spectrum when the color change occurs. We here propose an
electronic model consistent with all observed color behaviours, based
on the premise that yellow is the stable color whereas green is the
metastable one. The chameleon effect is possibly linked to a
nitrogen–hydrogen complex.
Diamond & Related Materials 16, 401-408