14ft Outlines of the Mineralogy and Geology 



Chymical Character, 

 It is infusible before the blowpipe. 



Geological Situation and Localities. 



It occurs in Argillite, in veins of various thickness, from that 

 of writing paper to the fourth of an inch. Sometimes very thin 

 lamina may be procured, six or eight inches square ; these often 

 divide the Argillite into rhoraboidal tables ; at the slate quarries 

 in Charlestown, also massive and disseminated in Amygdaloid at 

 Brighton. 



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Subspecies V. — Concreted Carbonates of Lime. 



Calcareous Incrustations. Cleaveland, p. 168. 



These are without difficulty reduced to any distinct varieties. 

 Their colour varies from white and yellowish white to wax 



\ 



yellow. 



. • 



They occur dendritick, ramons, in plates and in various imi- 

 tative forms, investing Argillite and Greenstone. Frequently 

 they resemble the forms assumed by drops of water or oil, when 

 gently pressed between two plates of glass. In their other char- 

 acters they resemble the preceding subspecies. 



Geological Situation and Localities. 

 They occur incrusting Greenstone and Argillite at Charles- 



town and Med ford. 



Subspecies VI. — Brown Spar, 



Brown Spar, Cleaveland, p. 17|. Foliated Brown Spar, Jameson, vol. i 

 p, 511. Sidero-calcite, Kirwan, vol, i. pu 105, 



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