Browse Items (1651 total)

The metasomatised pyroclastics are from the farm Thysfontein. They are baked and well indurated. Induration is the hardening of rocks by heat or baking as well as the hardening of sediments by cementation or compaction. The pyroclastics are…

This is dolerite from the "Dragon's Back" dyke, from the farm Romance. It is the youngest dolerite body in the area and contains biotite and hornblende. Emplacement of this dolerite took place at a much deeper crustal level than the gabbros. It has…

This is a volcanic breccia from the farm Murrelfontein adjacent to the contact with the gabbro unit. It includes partially melted glass and tridymite, a high temperature polymorph of quartz, and has a brecciated appearance. The breccia has a …

OCR PDF of supplemental information for Karroo- Bird's River Petrographic Suite

Grain sizes sand to silty sand, rounded and angular with very minor examples of weathering and thin quartz vein present. Collected from the same quarry as FR-2. (FOV: 1.28mm)

Grain size is fine sand to silty sand, mostly angular with some rounded crystals. Various shades of surficial weathering with distinct pockets of orange-brown oxydation. Fresh surfaces brown-green in color. Collected from same quarry as sample FR-1.…

Red jasper matrix with interescting veins of while quartz. Prominent physcial weathering, brittle areas fall apart to the touch. Several prominent fractures run through the rock, contributing to the weakened structure. Most fresh surfaces are reddish…

Fresh surfaces are dark blue in color, while weathered surfaces range in shades of green. Asbestos veins intersect throughout the rock, making up ~5% of the crystal mass. (FOV: 1.28)

Angular, silty size gains, composed of equal parts quatz, feldspars and rock fragments. Prominent orange and brown surface oxydation on all samples. Some samples contain evidence of bedding planes. Calicte is found along bedding planes, as well as…

Holocrystalline, medium grained, anhedral, ophitic, dibastic crystals. Low silica percentage (46.3%) for a Diabase, bordering on ultramafic compostion. Calcite is present on weathered surfaces, but not on fresh surfaces. (FOV: 3.2mm)

Angular sand size grains, dominated by quartz, have a brown color with a greenish tint. Calcite found on weathered bedding planes after lithification. Slight folding of the bedding planes in one direction. (FOV: 1.28)

Groundmass dominated by grey calcite and dolomite. Calcite and dolomite crystals are subhedral in thin section and hand sample.. (FOV: 1.28)

Fresh surfaces contain grey-white, anhedral calcite and dolomite crystals. Weathered surfaces are dark brown, with a fine powder observable after handling in hand sample. Bubbles from acid reaction turn dark brown on weathered surfaces. These…

Coarse sand grains made of quartz, surrounded by smaller feldspar grains. Greenish blue surface color, minimal surface weathering.

(Thin section FOV: 1.28)

More orange in color that FR-3 (Red Chert). Radiolaria fossils are visible in thin section amongst red-orange martix.

(Thin Section FOV: 1.28)

Sand sized quartz grains and smaller feldspars make up the matrix. Grey-brown sand weathers to a rusty golden color.

(Thin Section FOV: 1.28mm)

Equal mix of angular and rounded sand-sized grains of quartz, with clay sized feldspars. Surface contains significant coverage of calcite that formed after lithification. Fresh surfaces do not effervesce with acid meaning that reaction is based on…

Clay sized feldspars and quartz present, but majority of crystal grains too small to identify in thin section. Surface contains some calcite that formed after lithification. Fresh surfaces do not effervesce with acid meaning reaction is caused by…

Hand Sample: Aphanitic vesicular dark gray-black basalt. Sample contains numerous vesicles ranging in size from 0.01cm to 1.5 cm.

Hand Sample: Apahanitic vesicular dark gray-black basalt. Larger (