EXAMINATION OF A CALCAREOUS STONE. 3()1 



to be in some measure neglected ; so that it is not unusual 

 for persons, who understand the composition of the diamond 

 or other valuable gems, to walk in their fields, and pick up 

 many stones, the nature and use of which they are unac- 

 quainted with, though perhaps in a friable state composing 

 considerable part of the soil of which they are the proprie- 

 tors. And I believe in cases where the more common mine- Even those that 

 rals have formerly undergone examination, such is the pre- j^^^ fornTeri" 

 sent improved state of chemistry, and the consequent greater should be exa- 

 number and purity of tests and reagents, that it will scarcely 

 be deemed superfluous, to subject them to fresh investiga- 

 tion ; particularly if it be done with an ardent view to inqui- 

 quirj'', and with diligent care and attention to the results. 



Influenced by these considerations, I have ventured upon Thunder pick 

 an analysis of a stone of the calcareovis species, frequently ^^'^"^^'^* 

 met with in this country, and called by the common people 

 thunder pick, from the supposition of its falling from the 

 clouds in storms of thunder and lightning. It occurs in 

 crystals weighing from 10 to 1000 grains, of a conic shape. Crystals, 

 with a cavity at the base extending about a fourth part 

 down the centre of the ciystal. Its colour varies from gray, Colour. 

 brown, brownish red, to almost black, semitransparent. 

 The nearer they approach to the red colour, the greater is 

 their transparency. I cannot find they abound in any par- Generally soli. 

 ticular place, but are generally discovered solitary by the ^'■' ' 

 husbandmen when at plough, or turning up the earth by 

 ditching or otherwise. When scratched with a knife it has Smell. 

 a strong alliaceous or urinous smell. Its cross fracture is Fracture. 

 fibrous, with the strise diverging nearly as from a common 

 centre. Its longitudinal fracture is glittering, with the striae * 

 parallel. It is moderately hard, and of the specific gravity Spec, gravity. 

 of 2-663. 



a. When heated upon charcoal before the blow-pipe, its Infusible 

 colour disappears, but it is infusible. alone, 



b. With phosphate of soda it is difiicultly soluble and Fusible with 

 fuses into an enamelled bead. pl-osphate of 



soda, 



c. With borate of soda it dissolves more readily, and fuses with borax, 

 into a semitranslucid white globule. 



d. With caustic soda I could only partially fuse it into, a and partially, ^ 

 white enamel. ^'^*^ "''>• 



Exp. 



