270 
DESCRIPTIVE MINERALOGY. 
t 
TABULAR SPAR. 
Schaalstein. Clcaveland .— Spath en Tables, Wollastonite. Hauy. — Wollastonite, or Prismatic Augite. Jame¬ 
son. — Prismatischer Augit-Spath. Mohs. — Bisilicate of Lime. Thomson, (who describes a new Wollasto¬ 
nite.) — Wollastonite. Beudant. — Tabular Spar. Phillips, Shepard and Dana,. 
Description. Colour white, with a shade of grey, yellow, red or brown. It occurs in granu¬ 
lar and lamellar concretions; also massive and disseminated. The primary form is a right 
Fig. 184. (or oblique) rhombic prism. Fig. 184. M on M / 95° 20b Principal 
cleavages parallel to the planes of the primary. Fracture splintery. 
Lustre pearly vitreous. Translucent to opaque. Brittle. Hardness 
from 4.5 to 5.0. Specific gravity from 2.80 to 2.90. Before the 
blowpipe, it melts with difficulty into a semi-transparent colourless 
enamel; with borax, it fuses easily into a transparent glass. It forms 
a jelly with muriatic acid, and the solution, after the separation of the 
silica, gives an abundant precipitate with carbonate of ammonia ; and 
it may thus be distinguished from carbonate of lime, gypsum and 
tremolite, each of which tabular spar sometimes resembles. 
Composition. The results of all the analyses that have been made of this mineral, concur 
in showing that it is a bisilicate of lime, but it is never free from small quantities of foreign 
matter. According to Stromeyer, it contains silica 51.45, lime 47.41, oxide of iron 0.40. 
Formula Ca + 2SiO s . 
Geological Situation. It occurs in primitive limestone, in various parts of northern New- 
York. 
LOCALITIES. 
Essex County. At Willsborough, nine miles northwest of Essex, this mineral forms the 
sides of a powerful vein of garnet which traverses gneiss. It occurs in cleavable masses, 
white and translucent. A specimen from this locality was analyzed by Mr. Vanuxem.* Its 
composition was as follows : 
Silica,. 51.67 
Lime,. 47.00 
Oxide of iron,. 1.35 
In the town of Lewis, about ten miles south of Keeseville, tabular spar is found in abun¬ 
dance, with similar associates as at the last named locality. The garnet exhibits various 
colours ; it is massive, and in grains, forming the variety called colophonite. The tabular spar 
is very friable, and has a white or yellowish white colour. 
Journal of the Academy of Natural Sciences of Philadelphia. II. 182. 
