Browse Items (264 total)

Hand Specimen Reddish brown rock. Medium sand grade.Round to sub-round grains of quartz, often with a thin rim of red hematite. Mainly reddish and pink-brown grains, fewer white grains and very few black grains. Well sorted and well cemented.No…

Hand Specimen Mainly medium sand (to coarse sand in the case of L327a). Yellow-brown iron stained quartz, cemented by the same yellow brown oxide. A few larger quartz grains up to 5 mm long. Grains are angular to sub-rounded, and poorly…

Hand Specimen Dark grey rock, mainly fine sand.Does not react with acid, probably mainly quartz. Some glints of mica. Cement reacts with acid, so it is at least partially carbonate. Band of brown-grey material is due to…

Hand Specimen Superficially specimens “a” and “b” look very different due to their colours. L340a is pale grey, while L340b is dark purple-red. The colour of L340b indicates that it is ferruginous, containing significant quantities of iron…

Hand Specimen Very dark grey to black mudstone. Faint, fine-scale laminations visible on cut surface. Not fissile - does not readily split along bedding planes.Contains fossils and fossil imprints. Some glinting flakes of mica. This rock fizzes…

Hand Specimen Pale yellow-grey mudstone containing the fossil remains of a small arthropod with a segmented exoskeleton. The rock is banded and shows some surface discolouration due to weathering.Rock fizzes with acid, so contains carbonate. This…

Hand Specimen This white rock is virtually pure carbonate. It fizzes with acid. It is fine-grained and poorly cemented, making it soft and low density. It is commonly known as ‘chalk’. Thin-section Very uniform cryptocrystalline carbonate. Rare…

Hand Specimen Pale buff coloured, crystalline rock. Numerous cavities, thought to have been formed by shrinkage during alteration of primary calcite (CaCO3) to secondary dolomite (CaMg[CO3]2). There is a weak reaction to dilute acid, which…

Hand Specimen Grey-buff colour rock made up of ooids, mainly medium grained and spherical. Some shell and lithic fragments. Well compacted and cemented by calcite, which fizzes with acid. Thin-section The ooids look brown. They are made up of…

Hand Specimen This rock is made up of well cemented bioclasts. The bioclasts (mainly shell fragments) are poorly sorted, ranging from <1mm up to a few 10s of mm. Fine-grained cement fizzes with acid, indicating that it is carbonate. It has…