Lab Notes Gems & Gemology, Summer 2013, Vol. 49, No. 2

Fish-Like Inclusion in Fancy Yellow

This pavilion view of the 4.76 × 4.30 × 2.75 mm Fancy yellow diamond displays the “fish” inclusion scene. The fish appears to be facing to the right. Magnified 40×. Photo by Martha Altobelli.

It is always a pleasant surprise to find a new and interesting inclusion during routine observation. But an inclusion that reminds us of a particular shape, an effect known as pareidolia (Winter 2007 Lab Notes, pp. 363–364), is a geologic wonder.

The New York laboratory recently received a natural yellow (graded as Fancy yellow) “Cape” 0.51 ct rectangular faceted diamond exhibiting such a feature. Examination of the stone revealed a series of table-reaching fractures and clouds that seemed to form the outline and scale-like detail of a fish (pictured at top). The inclusion is large in relation to the stone, encompassing nearly 75% of the table.

Nearly all fractures in diamond result from the interaction among multiple cleavage directions (The Micro­World of Diamonds, Gemworld International, 2000, p. 97). While often detrimental to the value of a stone, this inclusion serves as a useful identifier, and such findings help keep the study of gems enjoyable.