20 ROGERS— NOTES ON PSEUDOMORPHS, [February 4. 



probably pseudomorphous after actinolite as it has the exact struc- 

 ture of the actinohte common in the schists of the Coast Ranges. 

 The mineral has a greasy feel and is scratched by the finger nail. 

 It is practically infusible and gives a little water in the closed tube. 

 Cleavage flakes give a negative biaxial interference figure with a 

 small axial angle. The axial plane is in the direction of the length 

 of the columnar crystals. 



16. ChrysocoUa after Cuprite. — (a) Santa Margarita Mine, 

 New Almaden, California {b) near Mammoth, Utah (Tintic dis- 

 trict). At both of these localities chrysocolla is pseudomorphous 

 after the chalcotrichite variety of cuprite, a variety that consists of 

 crystal aggregates of elongated cubes crossing and branching at 

 right angles. With polarized light, the chrysocolla exhibits an ag- 

 gregate structure and the outside surface occasionally consists of 

 concentric layers somewhat radiating. At New Almaden the cup- 

 rite occurs in seams in serpentine but it is believed to have its origin 

 in copper-bearing pyrite which occurs in a nearby prospect shaft. 



17. ChrysocoUa after Calcite. — (a) Arlington, N. J. (b) Reward 

 Gold Mine, Inyo County, California. Collected by Mr. C. E. 

 Oilman. 



(a) At Arlington chalcocite and secondary copper minerals occur 

 at the contact between diabase and triassic sandstone. The pseudo- 

 morphs were found in cavities of the sandstone. They consist of 

 small scalenohedrons (21^1) completely replaced by chrysocolla. 



(b) The Inyo County specimens are large prismatic quartz crys- 

 tals coated with a crust of chrysocolla. Some of the chrysocolla is 

 the form of acute rhombohedrons ( — 2R or 0221) with rounded 

 edges which represents, no doubt, original calcite. The chrysocolla 

 is made up of concentric layers, the inside ones of which are deeper 

 greenish blue than the outside. Under the microscope the fine 

 aggregate structure is in evidence. Associated cuprite is the source 

 of the copper. 



Petrifactions. 



18. Sphalerite replacing coral. — Galena, Kansas. A conical 

 coral, probably a Zaphrentis, 2 cm. in diameter, is replaced by dark 

 granular sphalerite. Most of the fossils from the chert of this 



