86 J. M. Clements — Study of Contact Metamorphism. 



and iron oxide. Various combinations of these minerals 

 occur, and likewise the textures vary. As a result of these 

 variations there are produced the different kinds of contact 

 products known as spilosites, desmosites, and adinoles. The 

 characters of the minerals showing nothing unusual, I shall 

 briefly describe the textures and mineral combinations which 

 characterize these various rocks. 



Spilosites — The ordinary spilosites are distinctly mottled in 

 the hand specimen, and show clearly to the naked eye in thin 

 section the oval spots which characterize them. These oval 

 areas are very commonly four millimeters long, and in rare 

 cases even longer. They are frequently connected, forming 

 chains. The spots are very appreciably darker than the mass 

 in which they lie, and are composed of aggregates of chlorite, 

 quartz, feldspar, and rutile, with a small amount of white mica. 

 The chlorite is the chief constituent of the spots and gives 

 them their dark color. The surrounding mass consists essen- 

 tially of white mica, quartz and feldspar, small epidote and 

 rutile crystals, flakes of hematite, and with a very slight amount 

 of chlorite. The different proportions of chlorite and musco- 

 vite cause the difference between the spots and the ground- 

 mass. In some of the spilosites we find a few flakes of biotite 

 and needles of actinolite. However, these are always very 

 subordinate in quantity to the chlorite. 



Other spilosites have been noted in this area in which the 

 spots are white and lie in a fine-grained dark mass composing 

 the greater part of the slides. So far as I can learn, only one 

 similar instance of the occurrence of such a variety of spilosite 

 has been described. This is by Van Werveke, to whose de- 

 scription reference is made by Zirkel* and Rosenbusch.f 



The white spots are composed essentially of feldspar, with 

 only a minor amount of chlorite and epidote. The feldspar 

 grains are much larger than those which take part in the con- 

 stitution of the mass surrounding the spots. This surrounding 

 mass is made up of quartz, feldspar, chlorite, epidote, some 

 sphene, with sheaves of actinolite scattered through it. In one 

 section flakes of biotite were observed mixed with the chlorite, 

 though in very subordinate quantity. 



*Zirkel. Lehrbuch der Petrographie, 2d edition, vol. ii, 1894, p. 719. 



f Rosenbusch, Mikroskopische Physiographie, 3d edition, vol. ii, 1896, p. 1127- 



