Gemmological Characteristics Of Myanmar Amber And The Study Of Ant Inclusions

Among the most commonly used amber in the commercial market,amber from Myanmar（Burmese amber,also known as burmite）is one of the most geologically oldest.The 9.9 million years old Burmese amber is a time capsule of the Cretaceous period,preserving many organisms that are thought to be extinct by now,including some extinct ant species.Modern ants are one of the most abundant and widely distributed animals on earth,but back in the Cretaceous period,ants were just beginning to diversify and were not as common.Many Cretaceous ant species were morphologically peculiar and were very different from their modern descendants.In this paper,Burmese ambers with ant inclusions were studied.To show that ant inclusions can be used as a diagnosis for the authentication and identification of the age and origin of amber,Standard gemological tests and infrared spectroscopy were used to confirm the amber samples are indeed Burmese amber,followed by in depth observation,description and identification of the ant inclusions by standard gemological microscope.Results from standard gemological tests shows that all samples has typical gemological characteristics of Burmese amber:all samples display typical interference colour under crossed polarized scope,refractive index of 1.54,uneven bluish-white fluorescence under long wave ultraviolet light and inert to weak purplish-blue fluorescence under short wave ultraviolet light,specific gravity of between 1.02～1.06,all samples are buoyant in the salt saturated solution bouyancy test and unreactive to the alcohol solvent test.The infrared spectra of all the samples show typical fossilized resin absorption peaks in the regions of 1724～1718cm^-1,1455～1450cm^-1,and 1377～1374cm^-1,and in the regions of 1227～1223cm^-1,1150～1132cm^-1,and 1031～1022cm^-1,they show the characteristic triplet absorption peaks that are typical to Burmese amber.Observation of the ant inclusions shows that all ants possess typical features of Cretaceous ant species such as,metanotum with a well-developed dorsal sclerite,long antennae with a relatively short scape,and,long and slender legs with pretarsal claw with subapical tooth.Among the identified Cretaceous ant species,ten of the ants belong to the genus Gerontoformica;all shows the presence of an uninterrupted row of peg-like denticles on the anterior margin of the clypeus and falcate mandibles with bidentate apex.Another two ants possess unique vertically articulated scythe-like shaped mandibles with single apical tooth,a morphological feature found only in the tribe Haidomyrmecini;one of them being identified possibly as Haidomymex zigrasi,which has only been found in Burmese amber,the other Haidomyrmecini is an unreported new ant specie,probably belongs to the genus Ceratomyrmex.Identifying Cretaceous ant inclusions to genus level can be an important evidence for the diagnosis of Cretaceous amber,minimizing the possible origins to Cretaceous amber producing countries where ant inclusions have been found:Myanmar,Russia,France and Canada,and identification to species level can even further confirm the exact origin of the amber.In the study of amber,identification and classification of organism inclusions can be an important non-destructive diagnosis for its age,origin and authenticity,an approach that can be used more widely in gemology.