290 THE TRAP MINERALS OF NOVA SCOTIA—GILPIN. 
cavities holding liquids, probably water holding some mineral in 
solution, or some hydrocarbon compound. 
Among the second group may be mentioned—Chalcedony. 
This is a wax-like translucent variety of quartz, frequently 
found filling fissures in the trap and in botryoidal forms, and 
containing minute cavities lined by pellucid quartz crystals of 
almost microscopic size. When of a clear red colour it is called 
Carnelian. It is also found gray, brown and faint shades of 
blue and green, and is presented under various names, such as 
Plasma, Prase, Heliotrope, ete. 
In Pliny’s time, the Jasper included all these varieties except- 
ing Carnelian. 
Agate. This may be considered a variegated chalcedony, the 
colours being banded, clouded, or due to visible impurities, and 
are caused by traces of organic matter, iron, manganese, ete. Spe- 
cimens of great beauty are found at nearly all points along the 
Bay shore, and sometimes weigh as much as 100 lbs. It is fre- 
quently noticed in little veins and strings. 
Onyx and Jasper also occur abundantly, beside many varieties 
arising from mixtures of these substances. 
Opal. This variety of quartz is a form of lower hardness, lesser 
specific gravity, and not possessed of capability of ecrystalliza- 
tion. The precious opal has been occasionally found here, but 
of. small size. When of good colour it forms a valuable jem. 
Cacholong is a softer variety frequently occurring as a lining 
of cavities. Semi or common opal is also frequently met. One 
common form of the opal is that of the accumulation and par- 
tial consolidation by resolution of the silicious shells of infusoria, 
which consist essentially of opal silica. 
Among the Hydrous Silicates we may mention first the Peeto- 
lite group of the Bisilicates, represented by— 
Laumontite. This mineral is generally flesh coloured, some- 
times red, and both massive and crystalline. It is met here at 
Peter’s Point, Port George, Long Point, and at Margaretville 
coloured green by copper. 
—s 
