162 BULLETIN OF THE 



parties the quartz in the ottrelite, but buts against the edge of the 

 crystal without altering its character or arrangement in proximity to it. 

 Sometimes the quartz grains fill the interior of the ottrelite in hour-glass 

 shape, but this form has no connection with twinning as in the case fig- 

 ured by Kosenbusch (Mik. Physiog., Vol. I. Plate XXII. Fig. 6), but is 

 evidently a case of crystal growth analogous to the forms so well known 

 in the augites of some eruptive rocks : a skeleton crystal of ottrelite 

 first formed, which did not enclose or else assimilated the quartz, while 

 a later growth, which filled out the double funnel-shaped cavity, was 

 able or obliged to enclose it. In the rock next to be described there 

 are skeleton crystals of ottrelite only partially filled up with the quartz- 

 bearing mineral. 



The black plates in this rock are somewhat smaller than those of 

 ottrelite, with a jagged outline. They have sometimes a spindle-shaped 

 cruss-section, indicating then that they are discoid, but are generally 

 bounded by straight parallel lines; they are not transparent, but have 

 frequently a yellow leucoxene core, indicating titaniferous iron ore. 

 There is no doubt that they are ilmeiiite, as de+finnined by M. Renard 

 in the similar rocks of the Ardennes.-^ 



These ilmenite plates are generally bordered on both siues by a thin 

 sheet of chlorite, the base of which is parallel to the ilmenite. (The 

 similar ilmenite plates described by M. Renard are bordered by sericite.) 

 The plates are often entirely enclosed in the ottrelite crystals, some- 

 times one half in, the other half projecting out. The chlorite coating 

 disappears when they are found in the ottrelite, but they are then some- 

 times bordered liy a zone of ottrelite free from quartz inclusions, unlike 

 the rest of the crystal, of the same size and shape as the chlorite, sug- 

 gesting: that the latter was absorbed into the ottrelite when the crystalli- 

 zation took place. Small grains of titanite mixed with black ore are 

 scattered through the rock, and there are occasional prisms of tour- 

 maline. 



Ottrelite Grammcke. -^This interesting rock was found by ]\Ir. Dale in 

 a glacial boulder at " Paradise," Newport, R. I. 



The rock contains fragments of blue and white quartz, enclosed in a 

 dark gray micaceous cement, spangled with small plates of ottrelite. 



The slides show that the rock has undergone intense dynarao- 

 metamorphic action ; the large fragments of clastic quartz in polarized 

 light exhibit all stages of change from mere straining to breaking and 



1 He mentions the occurrence of these forms in PJiode Island ottrelite schist. 



