Jackson.] 320 



Chemical Analyses of Minerals associated with the 

 Emery of Chester, Mass. By. C. T. Jackson, M. D. 



Andesine. 



This mineral, formerly mistaken for granular Quartzite and Indian- 

 ite, constitutes two veins of from one foot to eioliteen inches in width, 

 occurring on each side of the great Emery vein in the South Moun- 

 tain. Where exposed to atmospheric influences, this mineral is white 

 and loosely granular like granular quartz, readily crumbling like sand 

 where it has long been acted upon by frost. In the river, below water, 

 it is of a greenish tint, and has the close granular fracture of wax, 

 little resembling the weathered mineral. 



Hardness 7.5, or between Quartz and Topaz. 



Specific Gravity 2.586. 



COMPOSITION. 

 NO. I. NO. II. 



Silica .... 60.00 62.00 



Alumina . . . 25.00 24.40 



Lime .... 3.50 3.50 



IMagnesia . . . 0.70 0.70 



Soda .... 8.07 8.07 



Water .... 1.00 1.00 



Trace of ox. Iron 



98.27 99.67 



Analysis No. 1. was repeated only on the Silica and Alumina. 



Diaspore. 



This mineral is found in the form of broad bladed and longitudi- 

 nally striated crystals, on the Emery of the South Mountain in Ches- 

 ter. It also exists in drupes of delicate elongated quadrangular 

 prisms in cavities, and in short, broad prismatic crystals, implanted in 

 the solid Emery, and presenting blue and violet tints, according to 

 the position of their planes. 



It is rather difficult to detach perfect specimens when the mineral 

 occurs attached directly to the solid Emery, but when separated by 

 the chloritoid, the masses containing good crystals can be broken off 

 without difficulty. From the name of the mineral, it will be under- 

 stood that it cracks or breaks readily, the Greek term signifying 

 cracked. Two analyses were made of the Chester Diaspore. No. 1 

 by my son, John C. Jackson, and No. 2 by myself 



Hardness 7 1-4, or a little harder than Quartz crystal. 



Specific gravity 3.39. 



