The origin of color in natural C center bearing diamonds

Research areas:

• Surfaces planétaires (2011 - 2016)

Year:

2013

Authors:

• Thomas Hainschwang
• Emmanuel Fritsch
• Franck Notari
• Benjamin Rondeau
• Andrey Katrusha

Journal:

DIAMOND AND RELATED MATERIALS

Volume:

39

Pages:

27-40

Month:

October

ISSN:

0925-9635

BibTex:

@article{WOS:000326363000005, author = "Thomas Hainschwang and Emmanuel Fritsch and Franck Notari and Benjamin Rondeau and Andrey Katrusha", abstract = "The properties of 152 natural diamonds with C centers - detectable by the absorptions at about 1344 and/or 2688 cm(-1) in the infrared spectra - were analyzed in order to better understand their origin of color. While such diamonds are generally thought to be yellow, type Ib natural diamonds are usually not so, but mainly orange-yellow, orange, brown, `olive{\&}#039; (a mixture of yellow with brown and/or gray with always a greenish component) and mixtures thereof. The only natural diamonds found to be of pure yellow coloration were - with very few exceptions - type IaA diamonds with a very minor Ib component, of cuboid-octahedral growth, often so-called re-entrant cubes. This was verified by the analysis of over 70,000 bright yellow and over 20,000 yellow-orange melee diamonds (i.e. diamonds weighing less than 0.20 cts) submitted for testing at the laboratory. In natural type Ib diamonds of octahedral growth the color is strongly influenced by vacancy-related defects that originate mainly from plastic deformation; natural type Ib diamonds of regular octahedral growth generally show distinct deformation-related strain and often some associated color zoning or `colored graining{\&}#039; along octahedral planes. None of the nickel-rich, C-center-containing natural diamonds included in this study showed any specific Ni-related absorption band in the visible range spectrum that had an influence on color. The ``olive{{\&}#039;{\&}#039;} to brown color in type Ib diamonds was found to be caused by a combination of continuum absorption with increased absorbance from the NIR to about 480 nm plus distinct NV- center absorption. (C) 2013 Elsevier B.V. All rights reserved.", doi = "10.1016/j.diamond.2013.07.007", extra = "PICL", issn = "0925-9635", journal = "DIAMOND AND RELATED MATERIALS", month = "OCT", pages = "27-40", title = "{T}he origin of color in natural {C} center bearing diamonds", volume = "39", year = "2013", }

Abstract:

The properties of 152 natural diamonds with C centers - detectable by
the absorptions at about 1344 and/or 2688 cm(-1) in the infrared spectra
- were analyzed in order to better understand their origin of color.
While such diamonds are generally thought to be yellow, type Ib natural
diamonds are usually not so, but mainly orange-yellow, orange, brown,
`olive' (a mixture of yellow with brown and/or gray with always a
greenish component) and mixtures thereof. The only natural diamonds
found to be of pure yellow coloration were - with very few exceptions -
type IaA diamonds with a very minor Ib component, of cuboid-octahedral
growth, often so-called re-entrant cubes. This was verified by the
analysis of over 70,000 bright yellow and over 20,000 yellow-orange
melee diamonds (i.e. diamonds weighing less than 0.20 cts) submitted for
testing at the laboratory. In natural type Ib diamonds of octahedral
growth the color is strongly influenced by vacancy-related defects that
originate mainly from plastic deformation; natural type Ib diamonds of
regular octahedral growth generally show distinct deformation-related
strain and often some associated color zoning or `colored graining'
along octahedral planes. None of the nickel-rich, C-center-containing
natural diamonds included in this study showed any specific Ni-related
absorption band in the visible range spectrum that had an influence on
color.
The ``olive{''} to brown color in type Ib diamonds was found to be
caused by a combination of continuum absorption with increased
absorbance from the NIR to about 480 nm plus distinct NV- center
absorption. (C) 2013 Elsevier B.V. All rights reserved.