199 
. 
Olivine is always present in considerable amount. It oc- 
curs in rounded crystals or grains, one or two millimeters 
or more in diameter. It is mostly fresh and sometimes 
clear, sometimes filled with minute black microlites producing 
a “schiller” structure. In many specimens of the rock the 
olivine shows prominent resorption-phenomena: along the mar- 
gin and cracks it is changed to a black metallic matter — 
probably magnetite — with irregular boundaries. Sometimes 
a whole olivine crystal has been changed in this manner with 
the exception of a few small, separated remnants. The outer 
part of the black zone contains numerous needles and bunches 
of actinolite which is sometimes accompanied by colourless 
augite in slight quantity. Round this zone of magnetite-actin- 
olite is found an outer fringe of finely scaled, colouriess or 
faint greenish mica sometimes containing half discoloured re- 
mains of brown biotite. In other cases the olivine may be im- 
mediately surrounded by fresh brown biotite. In less fresh spe- 
cimens of the essexite the olivine is often surrounded by a 
margin of serpentine, or it may be quite serpentinized. 
Augite of a more or less pronounced violet tint, and 
therefore probably titaniferous, is a constant component of the 
essexite. It occurs in about the same amount as the olivine. 
It is as a rule quite allotriomorphic and often contains the 
usual black microlites, these, however, are not uniformly dis- 
persed in the auzite but concentrated in patches. The extinc- 
tion angle c:c is large and exceeds 40°. Locally a little pale 
green uralite may be found in the margin of the augite-anhedra. 
In the more decomposed varieties of the rock the augite to- 
gether with the other ferromagnesian minerals has changed to 
aggregates of serpentine, chlorite, epidote, calcite etc. 
A brown hornblende with the absorption-tints and optic 
orientation of the barkevikite is found in smali amount in most 
of the essexite-specimens. It occurs in small short prisms or 
Shapeless grains mixed with the biotite-aggregates; sometimes 
