530 A POPULAR EXPOSITION OF THE 
of which an example is given in fig. 44. H. 5-5 (but much less in 
weathered specimens) ; sp. gr. 2°6-2°8. Easily fusible. 
Composition, essentially: silica 49, alumina 28, and lime 
23, the latter in part replaced by a little soda. Scapolite 
occurs in the Laurentian limestone-bands, as in Calumet 
Island on the Ottawa ; Grenville township, on that river, 
(Argenteuil County); Hunterstown in Maskinongé County, Fig. 44. 
C. E.; and Golden Lake (with graphite, &c., Mr. Murray: Report 
for 1854) in Algona township, Renfrew County,C. W. A peculiar 
mineral, or rather rock, of a peach-blossom-red colour, occurring in 
Lanark County, C. W., and known as Wilsonite, (after Dr. James 
Wilson of Perth,) is an altered or semi-decomposed scapolite contain- 
ing carbonate of lime and a little water. 
C4.— Fusible. Yielding water in the bulb-tube. 
Prehnite.—Green of various shades, generally pale, and sometimes 
colourless. Chiefly in botryoidal and globular masses with radiated- 
fibrous structure; or in closely aggregated, flat, prismatic crystals 
belonging to the Trimetric System. H. 6-6:5; sp. gr. 2°8.-3-0. 
Fuses easily, and with continued bubbling; and yields from 4 to 5 per 
cent. of water in the bulb-tube. Composition: silica, alumina, lime, and 
water. Prehnite occurs mest commonly in association with trap rocks, . 
and is occasionally found in the veins which traverse the Huronian 
formation on the north shores of Lakes Huron and Superior. On the 
south (and also on the north-west) shore of the latter lake, it occurs 
in great abundance, often closely associated with the native copper of 
that region. At Isle Royale a beautiful variety occurs in small water- 
worn, nodular pieces of a rich green colour and radiated-fibrous 
structure. The fibres radiate from many central points, and these often 
consist of a nucleus of magnetic iron ore. This variety is commonly 
known by the name of Chlorastrolite (signifying green star-stone.) It 
is considered by some observers to be a distinct species, as its sp. gr. 
(2°98-3°20,) is somewhat higher, and its amount of water somewhat 
greater. than that of prehnite. The former arises however from the 
intermixed iron ore (to the presence of which, also, the deeper colour 
is to be attributed,) and the latter I find to be exceedingly variable, 
Five specimens in selected fragments, yielded respectively the following 
per-centage of water ;—4°86, 5°51, 4:11, 4°18, 4°60. Chlorastrolite 
