MINERALS AND GEOLOGY OF CANADA. 117 
paratively rare, but some occur in the townships of Rawdon and 
Bastard, associated with crystalline limestone. They are usually some- 
what micaceous, and the imbedded pebbles consist of quartz, feldspar, 
(often decomposed), sandstone, and sometimes of limestone. The 
quartzites of Bay St. Paul, and those of Rawdon, contain garnets in 
great abundance, and pass into garnet rock. 
The beds of iron ore, also placed in this subdivision from their 
general association with the crystalline limestones and dolomites, belong 
partly and chiefly to Magnetic iron oxide, and partly to Specular iron 
ore—minerals of which full descriptions are given in Parr II. of this 
Essay. These ores occur in vast beds interstratified with the lime- 
stones and other Laurentian strata. In thickness they vary from a 
yard or two, to upwards of two hundred feet. Their more important 
localities are mentioned below. 
(ce) Anorthosites:—The term anorthosite was first employed by 
Prof. Sterry Hunt of the Geological survey, to designate the more 
purely feldspathic rocks of the Laurentian series. These rocks consist 
of a mixture of lime and soda feldspars—minerals forming several 
species (Labradorite, Albite, Anorthite, &c., see Part II), all of which 
belong to the Triclinic or Anorthic system of crystallization (Parr I.) 
The anorthosites make up in themselves a vast thickness of the Lauren- 
tian rocks, and cover surface areas of large extent. They appear, accord- 
ing to Prof. Hunt, to occupy a higher position than the orthoclase 
gneiss-rocks, although occasionally interstratified with subordinate 
beds of these, and also, though more rarely, with strata of quartz- 
rock. ‘Their structure is coarsely crystalline, or otherwise more or 
less compact ; and their marks of stratification are frequently obscure. 
‘They often contain laminar masses of hypersthene of a brown (or 
green) submetallic tint ; and when this mineral becomes somewhat 
abundant, the variety termed “hypersthene rock” originates (see 
Parr III.) Ilmenite or titaniferous iron ore (described in Parr IT) 
is also sometimes present. An immense bed, 300 feet long and about 
90 feet wide, occurs in a feldspathic rock of this series, near Bay St. 
Paul, below Quebec. These rocks are chiefly of a greyish blue colour, 
but some are white, and others exhibit a yellowish, greenish, or red- 
dish tint. All become opaque white by weathering. Many contain 
cleavable masses of lime feldspar or Labradorite (Part II.), or appear 
to be almost wholly made up of that mineral. In these, a fine green 
-and blue opalescence or play of colour is sometimes observable: as in 
