Hornfels

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.

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

Geolocation