268 



PROCEEDINGS OF THE AMERICAN ACADEMY 



xene, the destruction of which has given birth to, at least, three products ; 

 namely, chlorite, calcite, and quartz. The relative ages of these, as ex- 

 pressed in the accompanying paragenetic table, are as observed where 

 thtjy are all represented in the veinlets. In the breaking up of the 

 pyroxene combination, the iron, alumina, and magnesia, and part of 

 the silica were I'emoved, and went to form chlorite ; the lime, combined 

 with the foreign carbonic acid, — possibly, also, with some magnesia, — 

 remained as a pseudomorph : there is less positive evidence that the 

 substance occupying cracks in these pseudomoi'phs (and which is not 

 affected by a twenty-four hours' treatment with cold muriatic acid) is 

 quartz, and that it is pseudomorphous after calcite. 



The only remark to be made with regard to the native copper is 

 that it was observed only in the veinlets near the fissure vein, and as 

 being younger than the quartz. 



The parageuetic scheme for this rock should seem to be as follows : — 



(I) 



ORIGINAL MAGMA. 



(ly.) 



Ferhiu Oxide. l.fDrniing seams in the 

 rock, and layers in Mabb's 

 vein. 



Caloite (magnesian?) 

 + imiiellnciil sub.'stance 

 (ijuartz?) pseudi)ninr- 

 plioiis after pyroxene, 

 and alsu tilling veinletti. 



3. Quartz crystallized in tlie 



veinlets, and perhaps also 

 pseudomorphous after 

 calcite after pyroxene. 



4. Native lCnLORiTic(?) 



COI'PKB on SUBSTAXOK 



quarts in lynniiger than 

 veinlets. Iquartz in 



Mabb's vein. 



Changes in the Lower Parts of the Beds. 

 There is no variety of these rocks that has not undergone a greater 

 or less change. The least altered instance is that which forms the 

 " Greenstone range," in which the remnants of magma-base and part 



i 



