The technology to identify a gemstone’s geologic and geographic origins has improved in the last decade to the point where accurately pinpointing the locality has become a reality. Using emeralds from different mines in the Cordillera Oriental region of Colombia, some of them only a few miles apart, scientists can now discern minute differences in chemical composition and determine each sample’s point of origin by studying the chemical “fingerprints” in their chromophores. The chromophores are trace elements of vanadium, nickel, or magnesium and vary geographically as a result of interstitial fluid migration prior to precipitation.
After recognizing that within-site chemical homogeneity and cross-site chemical heterogeneity depended on the amount of chromophores in the crystal structure, the authors sought to find out if chemical heterogeneity between emerald mining localities was chemically unique and statistically provable based on chromophore components alone. Included in the study were emerald samples from the Muzo, Cosquez, and Guali mines of Colombia, plus the Campo Verdes and Carnaíba mines in Brazil, and the Chantete mine in Zambia. Consideration for sample inclusion in this study involved the history of the host rock chemistry on the skeletal crystal structure, the occurrence of trace elements that link emeralds to their point of origin, the subsurface geology, fluid-rock interactions and the geochemical processes leading to emerald formation.
The study concluded that element-based heterogeneity exists between the six emerald mining sites. Through the use of an Amray scanning electron microscope (SEM) coupled to an EDAX energy-dispersive X-ray spectrometer (EDX), statistically significant chemical heterogeneity between mine sites was revealed by a non-destructive test that preserved the integrity of the sample.
The technology to identify a gemstone’s geologic and geographic origins has improved in the last decade to the point where accurately pinpointing the locality has become a reality. Using emeralds from different mines in the Cordillera Oriental region of Colombia, some of them only a few miles apart, scientists can now discern minute differences in chemical composition and determine each sample’s point of origin by studying the chemical “fingerprints” in their chromophores. The chromophores are trace elements of vanadium, nickel, or magnesium and vary geographically as a result of interstitial fluid migration prior to precipitation.
After recognizing that within-site chemical homogeneity and cross-site chemical heterogeneity depended on the amount of chromophores in the crystal structure, the authors sought to find out if chemical heterogeneity between emerald mining localities was chemically unique and statistically provable based on chromophore components alone. Included in the study were emerald samples from the Muzo, Cosquez, and Guali mines of Colombia, plus the Campo Verdes and Carnaíba mines in Brazil, and the Chantete mine in Zambia. Consideration for sample inclusion in this study involved the history of the host rock chemistry on the skeletal crystal structure, the occurrence of trace elements that link emeralds to their point of origin, the subsurface geology, fluid-rock interactions and the geochemical processes leading to emerald formation.
The study concluded that element-based heterogeneity exists between the six emerald mining sites. Through the use of an Amray scanning electron microscope (SEM) coupled to an EDAX energy-dispersive X-ray spectrometer (EDX), statistically significant chemical heterogeneity between mine sites was revealed by a non-destructive test that preserved the integrity of the sample.
Abstracted by James E. Shigley
The technology to identify a gemstone’s geologic and geographic origins has improved in the last decade to the point where accurately pinpointing the locality has become a reality. Using emeralds from different mines in the Cordillera Oriental region of Colombia, some of them only a few miles apart, scientists can now discern minute differences in chemical composition and determine each sample’s point of origin by studying the chemical “fingerprints” in their chromophores. The chromophores are trace elements of vanadium, nickel, or magnesium and vary geographically as a result of interstitial fluid migration prior to precipitation.
After recognizing that within-site chemical homogeneity and cross-site chemical heterogeneity depended on the amount of chromophores in the crystal structure, the authors sought to find out if chemical heterogeneity between emerald mining localities was chemically unique and statistically provable based on chromophore components alone. Included in the study were emerald samples from the Muzo, Cosquez, and Guali mines of Colombia, plus the Campo Verdes and Carnaíba mines in Brazil, and the Chantete mine in Zambia. Consideration for sample inclusion in this study involved the history of the host rock chemistry on the skeletal crystal structure, the occurrence of trace elements that link emeralds to their point of origin, the subsurface geology, fluid-rock interactions and the geochemical processes leading to emerald formation.
The study concluded that element-based heterogeneity exists between the six emerald mining sites. Through the use of an Amray scanning electron microscope (SEM) coupled to an EDAX energy-dispersive X-ray spectrometer (EDX), statistically significant chemical heterogeneity between mine sites was revealed by a non-destructive test that preserved the integrity of the sample.
The technology to identify a gemstone’s geologic and geographic origins has improved in the last decade to the point where accurately pinpointing the locality has become a reality. Using emeralds from different mines in the Cordillera Oriental region of Colombia, some of them only a few miles apart, scientists can now discern minute differences in chemical composition and determine each sample’s point of origin by studying the chemical “fingerprints” in their chromophores. The chromophores are trace elements of vanadium, nickel, or magnesium and vary geographically as a result of interstitial fluid migration prior to precipitation.
After recognizing that within-site chemical homogeneity and cross-site chemical heterogeneity depended on the amount of chromophores in the crystal structure, the authors sought to find out if chemical heterogeneity between emerald mining localities was chemically unique and statistically provable based on chromophore components alone. Included in the study were emerald samples from the Muzo, Cosquez, and Guali mines of Colombia, plus the Campo Verdes and Carnaíba mines in Brazil, and the Chantete mine in Zambia. Consideration for sample inclusion in this study involved the history of the host rock chemistry on the skeletal crystal structure, the occurrence of trace elements that link emeralds to their point of origin, the subsurface geology, fluid-rock interactions and the geochemical processes leading to emerald formation.
The study concluded that element-based heterogeneity exists between the six emerald mining sites. Through the use of an Amray scanning electron microscope (SEM) coupled to an EDAX energy-dispersive X-ray spectrometer (EDX), statistically significant chemical heterogeneity between mine sites was revealed by a non-destructive test that preserved the integrity of the sample.
Abstracted by James E. Shigley
