Johnson and Warren — Geology of Rhode Island. 29 



b} T a much finer grained border. Traces of the original feld- 

 spar cleavage and twinning structures are often preserved in 

 the arrangement of the secondary minerals. On the whole 

 the areas appear to have enlarged somewhat and to have suf- 

 fered more or less recrystallization and rearrangement within 

 their borders. 



The olivine is now commonly filled with a brownish dust, 

 and has suffered from chloritic and actinolitic replacement 

 as in the previous type, except that the process has gone fur- 

 ther. Many olivine crystals about the chloritic areas have 



Fig. 8A. The sketch shows the relations of the minerals in the chloritic 

 type, o, Unaltered olivine, c, Chlorite lamellae replacing olivine ; com- 

 monly lie parallel to the basal cleavage, c', Fine chlorite aggregate replac- 

 ing the plagioclase ; only the edge of the area is shown, a, Actinolite 

 prisms replacing the olivine. The black is the ore ; note that the continuity 

 of the ore is broken. 



Fig. 3B. This shows the olivine (or actinolite) with the border of chloritic 

 material lying between it and the ore, being replaced by a fibrous or lamel- 

 lar serpentine, (s.) Here again the ore is broken and in places shows its 

 reticulate structure. 



been entirely replaced by chlorite as well as actinolite, and fine 

 examples showing various stages of replacement may be seen. 

 The continuity of the ore-matrix is more often broken in this 



