524 A POPULAR EXPOSITION OF THE 
less remote from these beds. Briefly, amongst other Laurentian lo- 
ealities of Garnet, we may mention the following :—Various spots 
along the Muskvka river, as the Lake of Bays, &c.; the townships 
_ of Marmora and Elzevir, Hastings County, C. W.; Barrie and other 
townships in Frontenac County, C.W.; Hull, Ottawa County, C.E. ; 
Chatham, Chatham Gore, and Grenville townships (dark red and 
hyacinth-red varieties) in Argenteuil County, C. E ; the parish of St. 
Jérome in Terrebonne County, C.E.; Rawdon township, Montcalm 
County, C.E.; Hunterstown, Maskinonge County, C. H.; &e. In 
some of these localities, (St. Jérome especially, see Sir William Lo- 
gan’s Report for 1853) the garnets are sufficiently abundant to be 
available as a polishing material in place of emery. Amongst the 
altered strata south of the St. Lawrence, Mr. Hunt has discovered 
certain white or light-coloured beds which exhibit the composition 
of a lime garnet. In the township of Oxford, one of these consists 
of irregular rounded masses of white garnet.—H. 7:0 ; sp. gr. 3°536 
—associated with serpentine; and at the Falls of the River Guil- 
laume in Beauce Couuty, the same substance forms a compact homo- 
geneous rock (See Mr. Hunt’s Report for 1856.) 
Idocrase.—This mineral is identical with Garneé in composition 
and general characters, but differs in crystallization. It occurs in 
modified square-based prisms and pyramids of the Dimetric system, 
at least when crystallized. In other respects it cannot be dis- 
tinguished from garnet. Idocrase has been found, - 
associated with crystalline limestone, in Clarendon 
township Frontenac county, C. W.; Calumet Island I 
on the Ottawa; and Grenville township, Argenteuil 
County, C. 5. Fig. 37. 
Tourmaline—Of various colours, black, brown, yellow, green, 
blue, and pale red; sometimes colourless. The black variety is 
commonly known by the name of Schorl. Tourmaline occurs in — 
modified three, six, nine, or twelve-sided prisms longitudinally 
striated, or in columnar or fibrous masses. The crystals are generally 
triangular on the cross fracture, owing tothe predominance 
of three prismatic planes ; and this character is usually 
sufficient to distinguish the mineral from other substan- 
ces. H. 6°5-7:5; sp. gr.3°0-3°3. The black, and most 
of the brown varieties fuse easily, the others, as a  Fiz.38. 
