PLATE II. 



Fig. 1. — This ami also the next figure are uiicr()pliotogra})lis of the second 

 modification of contact-metamorjiliosod limestone, wliich is usually 

 called lime-silicate horufcls. Ilvaite here occurs as black radiating 

 needles (l) appearing as if black iron ore were veiled in thin 

 membranes of colloidal silica. The membranes are probably of a 

 lime-silicate extinguishing light parallel to the direction of ilvaite 

 needles, and showing high birefringency. Pp. 10 and 22. Mag- 

 nified 50 diameters. 



Fig. 2. — The same as in fig. 1. The ilvaite forms acicular radiating needles, 

 and is opaque and submetallic, appearing just like stibnite for 

 which it has been taken. Basal cleavage is distinct as may be 

 seen in the sharp dismemberment of the needles. This is the 

 normal type of ilvaite in contrast to the one in fig. 1, and encloses 

 diopside (d), but is enclosed by calcite (c). P. 10. Magnified 50 

 diameters. 



Fig. 3. — This and fig. 2 as well as PI. IL figs. 1 and 2 are microphoto- 

 graphs of the third modification of the lime-silicate hornfels. The 

 rock represented is diopsidite, and the mineral diopside (cZ) builds 

 up the great bulk of the mass, sometimes showing traces of the 

 characteristic augite-cleavage. Chalcopyrite (p) ^^^^ up the inter- 

 stices left by diopside. P. 11. Magnified 50 diameters. 



Fig. 4.' — The same as in fig. 3. The mode of association of both diopside 

 and chalcopyrite shows that the first was corroded and dissolved 

 away, and then replaced by the latter. P. 11. Magnified 50 

 diameters. 



