J. P. Cooke, Jr., on some American Chlorites. 201 
Art. XIX.—Crystallographic Examination of some American 
. Chlorites ; by Jostan P. Cookg, Jr. 
TuRouGH ‘the kindness ‘of my friend Prof. Brush of New 
Haven, I have had the opportunity of examining some unique 
imens of the Chlorites from the well known locality at 
Pennsylvania. My ob- 
servations confirm in al- 
eralogie, tome i, pp. 433- 
451; but the perfection of the crystals at my disposal have en- 
abled me to obtain a greater degree of accuracy in my measure- 
ter in Massachusetts. 
Kéimmererite or Violet Chrome Chlorite—The purest crystals of 
this beautiful mineral have the form represented in fig. bg 
They are generally, however, macled and then appear as 1m fig 
Besides the basal plane O and. the planes of fundamental 
or less modified by the planes of hexagonal pyramids, but un- 
fortunately the last are so strongly striated and uneven as to 
Wholly indeterminable. The violet Kammererite is frequently 
Mixed with green clinochlore, which gives to the crystals a green- 
angles italicised are certainly accurate to a minute. In 2 
B, and B, we give angles measured on two I err ol a 
. che 
Second crystal and these are important as provin ee 
