1890.] Mineralogy and Petrogrphy. 173 
ite all traces of their fragmental origin were obliterated ; the rock be- 
came crystalline, and a few additional minerals were produced. The 
first occurrence of glaucophane as a consitutent of British rocks is 
noted by Blake ™ in an altered diorite from a quarry near the Anglesea 
Monument, Anglesea. The rocks consists of chloritized glaucophane, 
grains of epidote, a rutile quartz and calcite. The glaucophane is 
present in elongated prisms, which form a felt around epidote, and are 
included in the quartz. 

Mineralogical News.— Morphological and Physical Properties.— 
The possibility of the selection of half the planes of the monoclinic 
hemi-pyramid in such a way as to fulfill the conditions of hemihedrism 
as been shown by Williams.” If two of the planes intersecting in 
the plane of symmetry be allowed to develop to the exclusion of the 
other two, there results an apparent hemimorphism, which in reality 
satisfies all the conditions of hemihedrism. ‘The monoclinic plane of 
symmetry remains, so that the character of the hemihedrism is the ` 
inclined-faced. Planes belonging to this hemihedral form are ex- 
hibited in pyroxene from Piedmont, Orange, and St. Lawrence coun- 
ties, N. Y., and from Canaan; ome: tex babit i is aia hemimon 
Ina 


on parting planes in 1 several minerals. He describes rutile from the 
Urals in which the usual cleavage parallel to œ Po, is wanting, its 
place being taken by a parting parallel to $ Poo, but whether asa 
result of twinning or not, Miigge is unable to decide. The author 
thinks that this variety of rutile is identical with the mineral from 
Polk county, N. C., described by Des Cloizeaux as a dimorphous 
form of rutile. A garnet from Arendal, Norway, possesses cleavages 
parallel to the dodecahedral face, and contains acicular inclusions of 
cyanite with their oo Pæ faces parallel to the o O faces of the garnet, 
and their c axes parallel to the edges of these faces. The mineral occurs 
in a schistose dioritic rock whose hornblende constituent has a well- 
developed parting parallel to Pæ. Parting parallel to an octahedral 
face, in many members of the spinel group, is declared to be the 
result of polysynthetic twinning. Calcite, with a parting parallel to 
co P2, galena with twinning lamellze parallel to 40, and breunerite, with 
` —2R 2R as the twinning plane, are also mentioned. Boracite from 

11 Geol. Mag., 1888, p. 125. 
12 Amer Jour. Sci., Aug. 1889, p. 115. Cf. AMER. NATURALIST, Nov. 1887, p. 1025. 
13 Neues Jahrb. f. Min., etc., 1889, I., p. 231. 
Bull, Soc. franc., d. Min., IX., 1886, p. 184. 
