L141 Gabbro

Very dark grey, coarse-grained rock, typical grain size 1-2 mm. 
Main mineral phases are black clinopyroxene, greenish olivine and pale grey feldspar. The rock is cross-cut by a small number of hairline white veins.

Plagioclase feldspar 
- Tabular phenocrysts making-up ~50% of the rock. Characteristic lamellar twinning. Some are zoned.

Olivine 
- Phenocrysts have been extensively altered, rendering them almost unrecognisable. The olivine has decomposed to magnetite and serpentine. Relict olivine grains display characteristic curving cracks and euhedral form.

Clinopyroxene (augite) 
- Interstitial grains making-up ~35% of the rock. Poikilitic texture. Inclined extinction. Interference colours from first order pink to second order orange. Pale grey under plane polarised light. Some simple twinning.

Accessory minerals 
- Opaque, interstitial, probably magnetite.

Coarse grained → slowly cooled, intrusive. 
Hydrothermal alteration of olivine after crystallisation of the rock.

gabbro