PALLASITE. — CUMBERLANDITE. 77 



Biotite occurs as a secondary product iu connection with the magnetite. It is seen 

 forming a fringe about the latter, or joined on to some of its prongs, extending out into 

 the olivine grains. The color is dark reddish brown, and the mineral shows strong 

 dichroism and well marked cleavage. 



In the magnetite filling some cavities and fissures, a dark green isotropic mineral, of 

 irregular outline and unkno\vn characters, was observed.* This is regarded by myself 

 as a secondary mineral, formed like the liiotite, in connection with the magnetite. In 

 another section considerable earthy yellowish green and green aggregately polarizing 

 alteration pi'oducts were observed in connection with the feldspar and olivine. 



In all of the preceding sections the olivine is the predominating mineral. The feld- 

 spar crystals are confined to one side of the hill composed of this rock, and they are 

 therefore local, and not to be regarded as characteristic of the rock as a whole. 



No. 1005, from the same locality as the preceding, but nearer the middle of the hill, 

 shows a dark granular and crystalline groundmass m which, imder a lens, can be seen 

 olivine in yellowish green grains, magnetite, and clear greenish glassy actinolite with a 

 well marked cleavage. Dark green serpentinous masses occur in the rock in irregular 

 vein-like and nodular forms. The rock weathers to a dull brownish gray surface, while 

 immediately beneath the surface crust the olivine is decomposed to a yellowish brown 

 ferruginous earth. 



Section : The general structure of the section is the same as that of No. 998, without 

 the feldspar ; that is, lilce the more compact portions of the section of that specimen. 

 A certain amount of alteration, however, has taken place here. Thi^ specimen, like all 

 except those in the immediate vicinity of No. 1000, is free from feldspar. The olivine 

 grains are now separated in the majority of cases from the magnetite sponge by a narrow 

 film of a pale greenish actinolitic alteration product, which also separates these grains 

 from one another. The same product iu places traverses fissui'es in the olivine, and 

 replaces some of the smaller grains. The olivine further presents in part a cloudy, smoky 

 appearance, arising from a dark-colored staining, extending in fine lines parallel to a 

 crystallographic axis. This clouding extends sometimes over part only, and at other 

 times over the entire crystal. A greenish yellow serpentine replaces the olivine to some 

 extent, and extends in vein-like forms across part of the crystals. The actinolite in the 

 section is in minute elongated, irregular crystals, usually formiug an interlocked mass. 

 The olivine contains fluid, glass, and gas inclusions, as well as detached secondary 

 actinolite crystals. 



No. 1002 is macroscopically almost identical with No. 1005 ; but microscopically, 

 its olivine is less in amount, and the actinolite in better formed and larger crystals. 

 In many portions of the section the latter mineral appears in long-bladed crystals with 

 well marked longitudinal cleavage. In other cases wlien the crystals are cut across they 

 show the characteristic amphibole cleavage rhombs. They are colorless, and exhibit very 

 brilliant polarization colors. Some of the altered portions of the section are of a pale 

 greenish hue, and formed of an interlaced mass of fibres and non-polarizing particles — 

 the fibres being apparently actinolite. Other portions, more coarsely crystalline, show 

 dichroism, varying from a pale green to a pale yellow. 



* Dr. Geo. H. Williams tliouglit that this might be hcroynitc, a mineral which he had been especially 

 studying. Speeimcus of the rock were placed iu his bauds, but owing to the small amount of this mineral, 

 together with its high specific gravity, he was unable to isolate it from the magnetite. 



