PLATE XIII. 



Fig. I. Limburgite Dike. Ordinary Light. X 33. Crystals of 

 colorless olivine in a ground-mass of augite, magnetite 

 grains and brown glass. 



Fig. 2. Camptonite. Ordinary Light. X 33. A phenocryst of 

 augite appears in the lower left hand corner. The 

 ground-mass is made up of hornblende prisms, ir- 

 regular feldspar crystals (plagioclase) and grains of 

 magnetite. 



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