ALUMINA. 



341 



LABRADORITE. 



fFrom its having been first found on the coast of Labrador.] 



Opalescent Feldspar, var. of Feldspar. CUavcland. — Labradorite. Thomson, PhUijps and Shepard. — Poly- 

 chromatic or Labrador Feldspar. Jameson. — Polychromatischer Fcld-spath. Mohs. — Labradorite, App. to 

 Chabasie. Beudant, 



Fig. 324. 



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° 3(y ; 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 55.75, 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 MorJah, 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. 



• flmmons. New-York Oeological Reports, 1633. 



