oday, yellow diamonds are among the most widely encountered of the "fancy color" diamonds (figure 1). From 1998 to the present, GIA has issued grading reports on more than 100,000 yellow diamonds, by far the most common of the fancy-color diamonds submitted to our laboratory. In 2003, for example, 58% of the diamonds submitted for GIA Colored Diamond Grading Reports or Colored Diamond Identification and Origin of Color Reports were in the yellow hue. Nevertheless, these represented only 2.4% of all diamonds submitted for various grading reports that year. The dichotomy between being common among colored diamonds yet relatively rare overall has created a mix of information and sometimes erroneous assumptions about yellow diamonds. In addition, although information about their "origin of color" or unusual characteristics (see below) has been documented over the years, little has been published about their color appearance and its relationship to color grading (one exception being Hofer, 1998). This article presents data on more than 24,000 fancy-color yellow diamonds that were examined by the GIA Gem Laboratory during the years 1998 and 2003. While our main concern in this study was gathering information to characterize the gemological and spectroscopic properties of the entire population of samples, we were also interested in identifying any trends in size, color grade, or clarity grade among the yellow diamonds submitted to us that might be revealed over time. To that end, we selected a sample population from these two years separated by a five-year span. Following a brief review of the literature on the geographic sources, cause of color, and other physical properties of fancy-color yellow diamonds, this article will focus on expanding the published information about these diamonds by documenting and 88 YELLOW DIAMONDS GEMS & GEMOLOGY SUMMER 2005

oday, yellow diamonds are among the most widely encountered of the "fancy color" diamonds (figure 1). From 1998 to the present, GIA has issued grading reports on more than 100,000 yellow diamonds, by far the most common of the fancy-color diamonds submitted to our laboratory. In 2003, for example, 58% of the diamonds submitted for GIA Colored Diamond Grading Reports or Colored Diamond Identification and Origin of Color Reports were in the yellow hue. Nevertheless, these represented only 2.4% of all diamonds submitted for various grading reports that year. The dichotomy between being common among colored diamonds yet relatively rare overall has created a mix of information and sometimes erroneous assumptions about yellow diamonds. In addition, although information about their "origin of color" or unusual characteristics (see below) has been documented over the years, little has been published about their color appearance and its relationship to color grading (one exception being Hofer, 1998). This article presents data on more than 24,000 fancy-color yellow diamonds that were examined by the GIA Gem Laboratory during the years 1998 and 2003. While our main concern in this study was gathering information to characterize the gemological and spectroscopic properties of the entire population of samples, we were also interested in identifying any trends in size, color grade, or clarity grade among the yellow diamonds submitted to us that might be revealed over time. To that end, we selected a sample population from these two years separated by a five-year span. Following a brief review of the literature on the geographic sources, cause of color, and other physical properties of fancy-color yellow diamonds, this article will focus on expanding the published information about these diamonds by documenting and 88 YELLOW DIAMONDS GEMS & GEMOLOGY SUMMER 2005