A phenomenon resembling play-of-color was seen in a 4.13 ct unheated sapphire recently examined by the author.

The distinction of natural from cultured pearls traditionally has been based on X-radiography.

An HPHT-treated round brilliant diamond with an inscription that presents as a GIA report number is found to be inconsistent with the institute's report, previously issued for an untreated diamond.

Observing a water drop’s interaction with opal, as well as refractive index, can confirm a specimen’s hydrophane nature with less risk of breakage than total immersion.

An opal rough is immersed in water and treated with oil and Opticon to observe effects on transparency and play-of-color.

A report on the color treatment process for these intensely greenish yellow to yellowish green cultured pearls and the techniques for identifying them.

A comparison study was made between the yellow and white nacre of the gold-lipped Pinctada maxima oyster shell and 65 yellow cultured pearls.

Two pearls presented a unique challenge, as testing at three different gemological laboratories could not conclusively identify them as natural or cultured, determine a freshwater or saltwater growth environment, or specify the producing mollusk.

A large natural pearl discovered in an edible oyster offers insight to the scientific pearl community.

The centerpiece of this brooch is a 98.67 ct Melo pearl, believed to be one of the world's largest.

Transparent rhodonite is considered one of the most difficult of all gems to facet because of its perfect cleavage and brittle, uneven fracture.

Shows the conversion of limonitic residues to hematite in surface-reaching inclusions, a practical indication of heat-treated corundum.