greywacke graywacke

Plane polarised light. Glacial erratic from near Eastfield Farm (Grid Ref. NZ555133), Nunthorpe, N.E.England. A Glacial Erratic, probably Ordovician or Silurian in age and from either the Southern Uplands of Scotland or the Lake District. The ill-sorted sand grains in a clay matrix are the result of turbidity currents and the rock is known as a turbidite, in this case, a greywacke.

Cross polarised light. The rock consists of ill-sorted angular to subangular quartz grains within a groundmass of clay minerals, chlorite and carbonate. A green coloured chlorite particle is visible in the PPL section just below the centre. It is 0.5mm in length. A sandstone with more than 15% matrix clay minerals is known as a greywacke or graywacke.

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Plane polarised light. Glacial erratic from near Eastfield Farm (Grid Ref. NZ555133), Nunthorpe, N.E.England. A Glacial Erratic, probably Ordovician or Silurian in age and from either the Southern Uplands of Scotland or the Lake District. The ill-sorted sand grains in a clay matrix are the result of turbidity currents and the rock is known as a turbidite, in this case, a greywacke.	Cross polarised light. The rock consists of ill-sorted angular to subangular quartz grains within a groundmass of clay minerals, chlorite and carbonate. A green coloured chlorite particle is visible in the PPL section just below the centre. It is 0.5mm in length. A sandstone with more than 15% matrix clay minerals is known as a greywacke or graywacke.