62 



PEOCEEDINGS OP THE NATIONAL MUSEUM. 



VOL. 66. 



The faces of the crystals are all lustrous and brilliant but the 

 prismatic planes are striated vertically and somewhat rounded by 

 oscillation. 



The optical properties of this axinite are: biaxial, negative ( — ), 

 2V medium large, r<v moderate, a= 1.673, /3= 1.680, 7=1.684, 



7 — a =.011. In the granular portion of the 

 taxinite seam chalcopyrite. apparently con- 

 temporaneous, is intergrown with theaxinite. 

 Paragenetically the axinite is placed as con- 

 temporaneous with chalcopyrite, epidote, and 

 hornblende, and earlier than apophyllite. 



a yn 



Fig. 10.— Prehnite. Type i crys- 

 tal. Orthographic crystal 

 drawings. 



bril- 



The scarcity of quartz is rather a nota- 

 i)le feature of the Goose Creek assemblage 

 of vein minerals. This mineral, so common 

 elsewhere in association with zeolites in trap- 

 pean rocks, was seen only once in all the spec- 

 imens collected. In this instance it occurred 

 as combs of prismatic crystal grown out from 

 either wall of a vein. The crystals rested 

 upon a layer of chlorite. The individual 

 quartz crystals average 2 millimeters long 



by 1 millimeter thick and are transparent, colorless, and 



liant. They have the common habit, 



hexagonal prism terminated by a 



symmetrical hexagonal pyramid. 



The vein between the quartz combs 



is filled with coarse granular datolite 



w^hich preserves molds of the quartz 



crystals when they are broken out. 



The whole vein averages about 1 cen- 

 timeter wide. A single small cube of 



galena was seen in the chlorite under- 

 lying the quartz. Paragenetically 



the quartz is later than chlorite and fi«- h -prehnite, type 2 crystal elon- 



\.i.L\j K.^Kj.i.i,LMu io GATED ON THE 6 AXIS SHOWING CRYSTAL 



galena and older than datolite. habit and striation of c (ood. 



Prehnite is the most abundant of the vein minerals and occurs in 

 a variety of forms. 



In the lot of material collected from this locality in 1915 by Doc- 

 tors Merrill and Wherry, the prehnite exhibits the ordinary form, pale 

 green columnar crusts with botryoidal to ill-defined cockscomb 

 surface. This prehnite rests upon a layer of somewhat weathered 



