ALUMINA. 
341 
LABRADORITE. 
[From its having been first found on the coast of Labrador.] 
Opalescent Feldspar, var. of Feldspar. Cleavelancl. — Labradorite. Thomson, Phillips and Shepard. — Poly¬ 
chromatic or Labrador Feldspar. Jameson. — Polychromatischer Feld-spath. Mohs. — Labradorite, App. to 
Chabasic. Bcudant. 
Description. Colour grey, with splendent opaline reflections of 
brilliant blue, green, yellow, red and pear grey hues. It sometimes 
occurs crystallized, but is usually massive and disseminated. Primary 
form a doubly oblique prism. Fig. 324. M on P 94° SO' ; M on T 
115°; P on T 119°. Cleavage parallel to the base most perfect. 
Lustre pearly on the perfect cleavage faces. Translucent when in 
thin fragments. Brittle. Hardness 6.0. Specific gravity from 2.69 
to 2.76. Before the blowpipe, it behaves like feldspar. When in 
powder, it is soluble by digestion in muriatic acid. 
Composition. A specimen from Labrador — Silica 55. / 5, alumina 26 • 50, lime 11.00, 
soda 4.00, oxide of iron 1.26, water 0.50 ( Klaproth ). 
Geological Situation. This mineral was first observed on the coast of Labrador, as a 
constituent of syenite. It has since been found in Greenland, and in various parts of Europe. 
localities. 
Essex County. Labradorite is very abundant in this county. Its colour is smoke-grey 
of various shades, generally opaque, but often translucent, when the laminae are not more than 
an eighth of an inch in thickness. In the most perfect specimens there are two reflections of 
colour, a blue and a green appearing in two directions from the cleavage faces. The bronze 
or copper-coloured reflections appear in pieces which are weathered. The polished pieces 
form gems which are esteemed in jewelry.* 
Fine specimens of labradorite are found in the form of bowlders of various sizes, in the 
towns of Moriah, Westport and Lewis. 
As this is a matter of interest in connexion with the subject of drift, it may be stated, that 
bowlders of labradorite have been noticed in the counties of Lewis, St. Lawrence, Warren, 
Schoharie, Greene and Orange. In the latter they occur in several of the towns, and weigh 
from a few pounds to several tons. Some of the specimens have been polished, and are very 
fine. They usually reflect only the green and blue colours. 
Fig. 324. 
* Emmons. New-York Geological Reports , 1838. 
