360 On Metallic Minerals, 



demand particular attention — a portion of one in my pos- 

 session from the surface stratum near Kingston must have 

 been five feet long and two feet in its greatest circumference, 

 they are seldom very distinct, and generally occur in a 

 rubbly limestone on or near the surface. The terebratulae 

 appear to hold the lowest position in a fine semi crystalline 

 limestone. 



The minerals which have been noticed either imbedded 

 or disseminated in this formation, are likewise characteristic 

 of it. The earthy varieties are chert or hornstone, 

 basanite, chlorite, calcareous spar, and sulphate of strontian. 

 From the hardness and flinty aspect of some portions of the 

 strata they appear to be passing into chert, while well 

 characterized hornstone is occasionally seen forming 

 prominent concretions on the surface of the limestone. — 

 On the shore of Garden Island, opposite Kingston, concre- 

 tions of hornstone looking like blotches of tar or pitch, are 

 very conspicuous, they have even the pitchy lustre in 

 fractiu'e, the same as is noticed in the limestone at the 

 Marmora works, although there the pitchy resemblance is 

 not so perfect. Ovate convex concretions of basanite are 

 not uncommon — they are good touch-stones. A green 

 mineral, supposed to be an earthy chlorite, is often much 

 mixed up with the ingredients composing the lowermost 

 strata. 



Calcareous spar often forms narrow viens in the middle 

 and uppermost strata and rounded concretions in the 

 lowermost. 



Sulphate of strontian occurs like the foregoing, forming 

 spherical concretions in the lowermost strata. 



The metallic minerals are sulphurct of iron and sulphuret 

 of zinc, (black and yellow blende). The sulphuretof iron 



