Title
Hornfels
Alternative Title
Contact Rock
Identifier
KBR-15
Description
This hornfels was collected from a section of contact metamorphism immediately above the dolerite of the formation from the farm Murrelfontein. It has "spots" of quartz, most likely inverted from tridymite spherulites, in a matrix of devitrified glass with mullite and cordierite. It has an aphanitic- porphyritic texture and is holocrystalline. The ground mass is light gray and anhedral, medium-grained dodecahedral brownish gray phenocrysts make up 25% of the hornfel. Some small spots of bright red iron staining (~1 mm) occur. The phenocrysts are opaque in thin section.
Thin sections are shown in plain polarized light and cross polarized light at a magnification of 40x. The rock is 70% quartz and 30% opaques. The groundmass is quartz.
Thin sections are shown in plain polarized light and cross polarized light at a magnification of 40x. The rock is 70% quartz and 30% opaques. The groundmass is quartz.
Date
No date given.
Contributor
Western Minerals, Inc.
Is Part Of
http://www.geosciencecollections.milne-library.org/collections/show/17
Spatial Coverage
Karoo- Birds River, Eastern Cape, South Africa
Temporal Coverage
183-179 Ma (Jurassic)
Accrual Method
Purchased from Western Minerals, Inc.
Unit
Lesotho Formation
Number of Thin Sections
1