224 
DESCRIPTIVE MINERALOGY. 
Fig. 84, the contractee of Haiiy. g on i 112° 10'. 
Fig. 85, unimixte of Haiiy. g on s 127° 52' 30" ; s on s' 116° 15' 5". 
Fig. 86, trirliomboidale of Haiiy. P on m 149° 2' 11"; P on s 119° 2' 11"; m on s' or 
m' on s 154° 39' 13"; m on s or m' on s' 121° 32' 54". 
Fig. 87, soustractive of Haiiy. t on t 137° 39' 26"; c on r or c' on r 152° 6' 52". 
Fig. 89. 
Fig. 88. The primary rhombohedron, with the lateral edges replaced by two planes. P 
on r or r' 151° 2' 40". 
Also the twin crystals, Figs. 89 and 90. 
St. Lawrence County. Probably no part of the world has furnished more beautiful or 
interesting forms of calcareous spar, than the county just named. This will sufficiently appear 
when I state that crystals have been obtained from nine to twelve inches in diameter, with 
all the sides and angles perfectly finished. The usual colours of these crystals are white or 
straw-yellow ; they vary from transparent to opaque. They occasionally contain water or 
some other liquid, but it soon disappears, as the specimens are very liable to be cracked 
or broken by exposure to alternations of temperature. Mineralogists are indebted for the 
fine crystalline forms of calcareous spar for which this county is so celebrated, to the mining 
operations, which were commenced here in 1836, and actively prosecuted during the two 
