LIME. 
215 
CALCAREOUS SPAR. 
Chaux Carbonatee. Hauy. •— Calcareous Spar. Cleaveland and Phillips. — Calcareous Spar, or Rhombohedral 
Limestone. Jameson. — Rhomboedriches Kalk-Haloid. Mohs. — Calcaire. Bcudant. — (Thomson, Shepard, 
and Dana include all the varieties of carbonate of lime under the name of Calcareous Spar. I restrict the 
latter term to the regularly crystallized forms of carbonate of lime, and to those imperfect crystals or masses, 
which, by cleavage, yield the primary rhombohedron.) 
Description. Colour, of pure varieties, white; when impure, it is often tinged with vari¬ 
ous shades of yellow, grey, red, green, brown, and even black. Streak white and greyish 
white. It occurs frequently crystallized, and, of all known minerals, exhibits the greatest 
number of varieties of the rhombohedral series of crystallization. The primary form is a 
rhombohedron, having angles of 105° 5' and 74° 55 / (Fig. 55). When transparent, it is 
Fig. 56. 
Fig. 57. 
Fig. 55. 
doubly refractive, and is then of¬ 
ten known by the name of Ice¬ 
land Spar. The various secon¬ 
dary forms can easily be reduced 
to the primary, as shown in Fig. 
56 and 57. Lustre, when pure, 
splendent and vitreous. Hard¬ 
ness 3.0; scratches gypsum, but 
is scratched by arragonite. Spe¬ 
cific gravity from 2.50 to 2.80. 
Before the blowpipe, alone, it be¬ 
comes caustic lime, and shines 
with peculiar brightness as soon 
as all the carbonic acid is driven 
off; with borax or biphosphate of soda, it fuses with effervescence into a glass. 
Calcareous spar, as well as all the other subspecies under carbonate of lime, may be distin¬ 
guished from gypsum by its greater hardness, and by its effervescence in dilute acids. It is 
not so hard as fluor spar, and it does not, when its powder is thrown into warm sulphuric 
acid, yield a gas capable of corroding glass. It possesses a less specific gravity than the 
carbonates of barytes, strontian or lead, each of which it sometimes resembles. 
Composition. Specimen from Iceland —carbonic acid 43.70, lime 56.15 (Stromeyer); 
carbonic acid 43.05, lime 56.33 (Biot). Formula CaO.CCh. 
Geological Situation. Calcareous spar does not appear to be peculiar to any class of 
rocks. It is found in veins in the granite and gneiss both of northern and southern New-York, 
while it also abounds in almost all the limestones and slates in the central and western portions 
of the State. 
