In the majority of Leg 180 samples, it was clear that the main lithology is relatively barren of organic matter. For these, visible fragments of organic matter were handpicked, generally being extracted with a pair of tweezers. For these samples, the abundance of organic matter in the block examined is much greater than that for the average of the sample. With samples containing coal or abundant dispersed organic matter, part of the sample was crushed.
The handpicked or crushed samples were dried in a vacuum oven at normal pressure. A temperature of ~120°C was used in order to stabilize any swelling clays that were present and to minimize the problems associated with low-rank vitrinite that has a high moisture content.
Polished blocks were prepared by mounting the grains of the dried sample in polyester resin (ASTIC) to form "whole-rock" preparations. However, as noted, a high proportion had been handpicked so that they represented whole-rock mounts of selected material. Setting properties of the samples were generally good, with mounting problems being restricted to small number of highly pyritic samples. Normal grinding (silicon carbide papers) and polishing techniques (chromium sesquioxide [GNM grade], followed by magnesium oxide [grade Maglite D/E]) were used for the resin-mounted blocks.
Oil and oil drops are easier to identify in whole-rock mounts, but these proved to be rare overall. Additionally, within whole-rock mounts, identification of organic matter types is more certain because grain outlines and polishing relief are easier to detect. For low-rank vitrinite, use of whole-rock preparations allows observation of textural features free of the effects of demineralization. Organic matter assemblages can only be determined in whole-rock preparations.
Examination of samples in fluorescence mode permits the detection of liptinite macerals and discrimination of suberinite and fluorescing vitrinite. Fluorescence mode was available for making observations on the fields used for vitrinite reflectance measurements, and only small changes are required to change from fluorescence mode to reflected white light mode to use the photometer.