Exploration of Inclusion Characteristic and Formation Environment of A Kind of Petroleum-Bearing Quartz

Petroleum-bearing quartz (i.e. oil-bearing quartz) is popular in the international jewelry market for its unique organic inclusions with strong fluorescence. However, the types, assemblages of the inclusions and their genetic conditions are rarely studied. In this paper, a typical kind of gem-quality petroleum-bearing quartz on the market were analyzed by digital microscope system, Raman spectroscopy, microscopic Fourier transform infrared spectrometer and other gemmological test methods. The results showed that there are four types of inclusions in petroleum-bearing quartz: negative crystal-shaped three-phase inclusions, irregular three-phase inclusions, black solid-phase inclusions, and dry inclusions with craquelure-like inwall. The gas phase of the three-phase inclusions is methane (CH₄) mixed with trace ethane (C₂H₆); the colourless liquid phase is an aqueous solution dissolved with few methane, the yellow liquid phase is mainly alkanes with trace aromatics; the solid part of three-phase inclusions, the black solid-phase inclusions and the dry inclusions with craquelure-like inwall have the same composition: bituminous. The composition, colour and fluorescence characteristics of the three phase inclusions of the samples are consistent with petroleum-bearing quartz from Baluchistan, Pakistan. Combined with the inclusions and crystallographic characteristics, it is inferred that petroleum-bearing quartz is slowly crystallized in carbonate-type low-temperature hydrothermal deposits.