The outcrop width of the unit is 280 metres.

Exposed surfaces of the Luibean semipelitic schist show a grey brown colouration with a well developed foliation being observed with the foliation surfaces being defined by white micas and the surfaces being approximately 1 centimetre apart. The fresh surface of the rock varies according to whether the surface is a foliation surface or a section normal to the foliation surface. The section normal to the foliation surface is a grey colour overall but with lighter streaks being observed on closer examination. The grain size of the rock is variable between grains of less than 0.0625 millimetres (i.e. silt grade material) and grains of 1.0 millimetre (i.e. sand grade material). The grain size variation may suggest a sandy mudstone precursor. The "S" fabric is well developed, a poorly developed "L" fabric may be present but the minerals that define it cannot be distinguished. The rock has a schistose fabric with the alignment of white micas imparting glossy lustre to the foliation surfaces.

The mineralogy of the rock includes: quartz 35%, feldspar 35%, biotite 20%, white mica 10%.

The general strike of the foliation is to the Northwest - Southeast dipping steeply to the Southwest.

The north-eastern boundary is exposed at Location 144 (c.f. Garbh amphibolite). The south-western boundary could not be observed but was inferred as the point where Achlais amphibolite outcrop began.

No structures could be observed in this unit.