TAB. V. 



CALX sericea. 

 Satin Spar. 



Class 2. Earth. Order 1. Homogeneous. 

 Gen. 1. Lime. Spec. 2. Carbonate of Lime. 

 Div. 2. Imitative. 



My friend the Rev. Mr. J. Harriman first favoured me with 

 a piece of this curious mineral, about the year 1797. It was 

 then recently made known to the mineralogical world by 

 Mr. Stag, who sent me a piece soon after. It is understood 

 to have been discovered about ten years ago, about a mile 

 from Alston in Cumberland, washed by the river Tyne, near 

 the level of its bed, and no where else at present. The spot 

 is about 30 yards long and 10 yards wide ; the middle pro- 

 ducing the broadest stratum, which was about 4 inches, 

 soon narrowing and becoming full of veins. I was told it 

 was a very pure carbonate of lime soon after I received it, 

 although it was kept a secret where it was found. 



The colour is white, with a beautiful satiny lustre, showing 

 the strata broad in the light and shade, and innumerable in 

 the intermediate space, varying as they are directed to the 

 light, which is best if perpendicular to them. It transmits 

 light at the edges, or in thin pieces. The fracture in the 

 direction of the striae is fibrous, straight (perhaps with im- 



