"Black Sand" in the Drift North of Grey stones. 167 



In the samples of ''■ black sand " scraped from off the beach, one 

 large scale of gold and five smaller specks were found. 



From the sample of 7^ lbs. taken from the foot of the cliff, and 

 washed, thirty-seven specks of gold were obtained ; eighteen specks 

 in the finest portion, fifteen in that of the second degree of fineness, 

 and four in that of the third ; none being found in the two coarser 

 portions; it, therefore, appears that the gold is all very finely 

 divided. 



Gold was found in small quantities in all the specimens of 

 black sand taken from the beach. 



Black sands occur at other places along the east coast. In 

 the Museum of the Royal College of Science, Dublin, there is a 

 specimen of magnetic iron sand from Courtown, where, I believe, 

 it occurs between the mouth of the river and the promontory to 

 the south ; it also occurs at Ballymoney, north of the last men- 

 tioned locality, from which I obtained a specimen with the follow- 

 ing description of its occurrence : — 



" Black Sand, Ballymoney Strand, Co. Wexford. — From a mile to 

 a mile and a half N.N.E. of Ballymoney fishery a thin film of ' black 

 sand ' was observed in places lying on the ordinary fine sand of the 

 beach ; these patches always occurred in the immediate vicinity of 

 dykes and protrusions of gabbro, and in one place, on the weathered 

 surface of one of the gabbros, the black grains in situ were observed 

 as shown in the specimen. The black sand forming the other specimen 

 was skimmed from ofi'the surface of the fine siliceous sand." 



The question naturally arises where do these sands come from ? 

 Do their constituents occur in theimmediate neighbourhood in some 

 mineral vein or channel ? or do they occur widely disseminated 

 through the rocks which, by their disintegration, have furnished 

 this drift, and is their occurrence here in such a concentrated form 

 due to local causes ? 



The occurrence of the sand along such a limited extent of 

 shore suggests that the mother rock is in the immediate vicinity ; 

 and from the fact of magnetic iron occurring on the wall of a 

 gabbro dyke, at Ballymoney, it seems not improbable, that the 

 sand at Greystones may be derived from the vicinity of some of 

 the greenstone dykes that occur in the Cambrian rocks, two of 

 which are close at hand ; one seen in the railway cutting near 

 Greystones station, the other on the southern slope of Bray Head. 

 But, on the other hand, the associated minerals (quartz, feldspar, 



SciEN. Proc, K.D.S. Vol. hi., Pt. iv p 



