ST. LAWRENCE COUNTY. 
351 
they form large and important portions of a district, or of a geological system ; and the mine¬ 
ralogist necessarily describes them, because they are simple mineral substances, existing in 
some places as individuals, the power of crystallization having operated upon, or individual¬ 
ized them, to speak in the language of the crystal lographer. 
This substance, like hornblende, exists both in amorphous masses and in crystals. When 
in crystals, it has the form of pyroxene; an oblique rhombic prism, and a distinct cleavage 
parallel to P. Its hardness equals 3.5 to 4.0, and its specific gravity is 2.874. It is strongly 
coherent. Before the blowpipe, it fuses with difficulty into a white enamel. Moistened with 
nitrate of cobalt, it assumes a pale flesh-red. In this State, it is associated with primary 
limestone, usually in amorphous masses, with a crystalline structure, and sometimes in dis¬ 
tinct crystals. 
Crystals of this substance were first found in Canton, in limestone. In the limestone, upon 
its irregular surfaces, were many small slender crystals, possessing a regular cleavage. I 
state this fact, for the purpose of doing away the impression that these forms, although called 
crystals, might have been pseudomorphous ; for pseudomorphs never possess a regular struc¬ 
ture, or a cleavage. With these facts, it is clear that rensselaerite differs from soapstone 
or steatite, by its hardness ; it is softer than pyroxene, and is not a pseudomorph, in conse 
quence of possessing the requisite characters of a crystal. To these facts, I may justly add^ 
that it is not a mixed mineral like granite, consisting of soapstone and pyroxene. To the 
eye, even when assisted by the microscope, it is homogeneous throughout. If mixed, it 
cannot be shown by any mode of inspection ; and as analysis cannot demonstrate such a con¬ 
dition, we have full liberty to claim it as a simple mineral species. 
But this substance claims attention in this place as a rock, and as such I shall describe it. 
This mass, though it appears homogeneous, yet is often associated with serpentine and 
primary limestone ; but it does not, as a rock, form with either of these bodies a compound 
analogous to that of serpentine and limestone : it rather exists by itself. It presents a great 
range of colors, as white, grey, brown verging to black. Its structure is usually compact; 
the outside is more compact and whiter than the interior, which is often slightly crystalline ; 
but masses are often found which are crystalline throughout, like calcareous spar or sahlite. 
Rensselaerite resembles serpentine ; it forms irregular masses, rarely continuous over sixty 
or seventy rods. In some instances serpentine appears to pass into rensselaerite, and the 
connection is so intricate that it is difficult to draw a line of distinction between them. Rens¬ 
selaerite is never so hard but that it may be cut with a saw, and hence shaped into any desi¬ 
rable form. When cut into pieces a quarter of an inch thick, it is translucent; and if the 
mass is white, it has the agreeable translucency of porcelain. Like potstone, it is refractory 
in the fire, and is not liable to crack when heated suddenly. A strong white heat hardens 
and whitens the mass ; and in this respect it resembles soapstone, for which it may be sub¬ 
stituted. 
As a rock, rensselaerite belongs to the unstratified division of the primary system, occurring 
in masses similar to serpentine or granite. 
There is a locality of it in the town of Fowler, on the Belmont farm, extending irregularly 
