Nature 183, 485 (14 February 1959); doi:10.1038/183485a0

Heavy Minerals in Certain Old Red Sandstone and Silurian Limestones of Monmouth

C. B. CRAMPTON

Soil Survey of England and Wales, Rothamsted Experimental Station, Harpenden, Herts. Jan. 6.

THE Wenlock Limestone outcrops intermittently within the inlier of Silurian rocks situated between Usk and Pontypool, and the 'Cornstones'¹ as discontinuous bands within the Old Red Sandstone of Monmouth. Samples of both limestones were crushed, dispersed, and particles with a diameter greater than 0.2 mm. removed by wet sieving, and those with a diameter less than 0.02 mm. by decantation. The residue corresponding to fine sand contains the bulk of the heavy minerals which were separated in bromoform, identified, and their relative proportions determined by microscopic counts which have been combined in Table 1.

1. Heard, A. , and Davies, R. , Quart. J. Geol. Soc., 80, 489 (1924). | ChemPort |
2. Milner, H. B. , "Sedimentary Petrography", third edit., 393 (Murby London, 1952).