82 B. J. HARRINGTON ON 
The rocks in which the sodalite occurs require further study. One of them is a 
nepheline-syenite, closely resembling, both macroscopically and microscopically, some of 
those found near Montreal, while another, in which the sodalite appears to be most 
abundant, is a grey gneiss-like rock containing a great deal of quartz, and possibly 
fragmental. 
II. —HURONITE. 
The name “ Huronite ” was long ago given by Dr. Thomson, of Glasgow, to a mineral 
which was found ina boulder of diabase on Drummond Island, in Lake Huron, and 
which was sent to him by the late Dr. Holmes, of Montreal. Thomson regarded it as a 
new species and published a discription and analysis of it in his “ Mineralogy ” in 1836. 
Dana, in his “ Mineralogy,” speaks of it as “an impure anorthite-like feldspar,” but 
also includes it with fahlunite, on the authority of Hunt. Its true affinities are evidently 
with the feldspars, and it may be looked upon as an impure or altered form of anorthite. 
One of the original specimens from Drummond Island is in the Holmes collection at 
McGill College, and an examination of this shows that Thomson’s description is in several 
respects incorrect. The hardness, for example, is about 5} instead of 34, as stated by 
Thomson. Instead of being infusible, it is distinctly fusible (F about 5), while it contains 
alkalies, the presence of which is entirely ignored by Thomson. 
As we have seen, the mineral from Drummond Island was found in boulders, and the 
origin of these was not known. About two years ago, however, an exactly similar material 
was discovered in situ by Dr. Girdwood near Sudbury, Ontario, where it occurs in 
rounded or somewhat angular masses in a dark green dyke of diabase, possibly the source 
of the boulders on Drummond Island. The Sudbury mineral, like that from Drummond 
Island, is of a light yellowish green colour, shows somewhat indistinct cleavage, and in 
places, faint striæ, which are probably due to multiple twinning. It is translucent on the 
edges, and has a rather waxy lustre. The hardness is 54, or a little over, fusibility about 
5, and specific gravity 2.814. Under the microscope, thin sections give evidence of 
considerable alteration, but with polarized light, the banding due to twinning can be seen 
in places. An analysis made by Mr. Nevil N. Evans, chemical assistant in the laboratory 
of McGill College, is given under I., while Thomson’s is’given under [1.— 




CoNSTITUENTS. Ts ie 
SN Da8avebt once doactoneno dc 47.07 45.80 
AÏUMIN AR ee cbr screens rer ce 32.49 33.92 
Ferric Oxides... ----crrrre 0.97 | FeO 4.32 
MEME AS res eces CL AAC 3.30 8.04 
Mapnesias..t aoa ood d0D adoose | 0.22 1372 
IPOtaR he ut rec cotes re De CS M EE T2 
Od EVORSSÉ ER mectteeretlo 2. OB. MS RS a see 
Boss OnAgnitIon. --.------ ee 2279 4.16 
TOTAT:--Cererr cer 101.68 97.96 
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SPOCTACROTAVIEY ieee atocietelersiereielete 2.814 2.8625 





