When we think about phantoms as inclusions, quartz typically comes to mind. However, this Quarterly Crystal is a bit different, in that the phantom examined resides in a well-formed, transparent octahedral diamond crystal reportedly from the De Beers mine in the Republic of South Africa (figure 1). The colorless diamond host measures 8.26 × 6.20 × 5.37 mm, weighs 2.22 ct, and was purchased from David New in 1989 in Tucson, Arizona.
As shown in figure 2, the phantom is a most unusual octahedral orangy red-brown limonitic crystal formation showing trigons and dark green radiation stains on its inner surfaces. The triangular faces of the phantom were likely once composed of an iron sulfide, such as pyrrhotite, which was subsequently altered epigenetically to limonite, a rusty mixture of hematite and goethite.
The complete phantom is visible through each of the eight octahedral faces of the diamond host. We have never encountered anything like this unique diamond crystal, nor does the literature on diamonds contain any such descriptions of similar phantoms.
John I. Koivula is analytical microscopist, and Nathan Renfro is senior manager of colored stone identification, at GIA in Carlsbad, California.
When we think about phantoms as inclusions, quartz typically comes to mind. However, this Quarterly Crystal is a bit different, in that the phantom examined resides in a well-formed, transparent octahedral diamond crystal reportedly from the De Beers mine in the Republic of South Africa (figure 1). The colorless diamond host measures 8.26 × 6.20 × 5.37 mm, weighs 2.22 ct, and was purchased from David New in 1989 in Tucson, Arizona.
As shown in figure 2, the phantom is a most unusual octahedral orangy red-brown limonitic crystal formation showing trigons and dark green radiation stains on its inner surfaces. The triangular faces of the phantom were likely once composed of an iron sulfide, such as pyrrhotite, which was subsequently altered epigenetically to limonite, a rusty mixture of hematite and goethite.
The complete phantom is visible through each of the eight octahedral faces of the diamond host. We have never encountered anything like this unique diamond crystal, nor does the literature on diamonds contain any such descriptions of similar phantoms.
John I. Koivula is analytical microscopist, and Nathan Renfro is senior manager of colored stone identification, at GIA in Carlsbad, California.
