No. 8. — Contributions from the Petrographical Laboratory of the 
Harvard University Museum. 
lite 
On some Occurrences of Ottrelite and Ilmenite Schist in New England. 
By J. E. Wourr. 
In the series of metamorphosed sediments which, in the many locali- 
ties, represent nearly every geological horizon, a wide-spread type of rocks 
are characterized by their fine grain, glistening micaceous aspect, and 
perfection of cleavage, to which the names of phyllite, micaceous slate, 
argillaceous mica schist, etc. have been applied. They represent 
original fine-grained argillaceous sediments, in which the metamorphic 
development of new minerals combined with the production of cleavage 
has partially or totally changed the original character. These rocks 
frequently attract attention by the presence of porphyritic, more or less 
perfectly shaped crystals, scattered through the fine-grained micaceous 
paste, which, unlike the analogous crystals of porphyritic eruptive rocks, 
appear to have formed /ater than the “groundmass.” Garnet, biotite, 
andalusite (chiastolite), staurolite, albite, magnetite, ilmenite, and min- 
erals of the ottrelite group, occur in this way. In this paper some 
notes are presented on schists or phyllites containing ottrelite or 
ilmenite plates. 
Ottrelite or chloritoid schists of Archean, Cambrian, Carboniferous, 
and perhaps of later age, have been described from numerous localities 
in Europe. The Cambrian phyllites of the Ardennes, among which the 
classical ottrelite schists occur, have undergone a thorough chemical and 
microscopical investigation by M. Renard.! One of these rocks is of par- 
ticular interest in this connection, namely, the “Phyllade a ilmenite des 
Forges de la Commune.” The bluish gray rock contains numerous small 
glittering metallic plates which can easily be mistaken for ottrelite ; in 
the section they are transparent on the thin edge, with a brown color, 
1 Bull. Mus. R. Hist. Nat. Belg., Vol. I. pp. 212-249, Vol. II. pp. 127-152, 
Vol. III. pp. 84, 85, 230-268. 
VOL. XVI. — NO. 38. 
