2 BULLETIN 149, UNITED STATES NATIONAL MUSEUM 



and augite; the plagioclase feldspars anorthite, lahradorite, or oligo- 

 clase; the phosphate apatite; the oxides magnetite, chromite, and 

 guartz; the sulphides troilite and pyrrhotite; rarely the carbonate 

 hreunnerite and various forms of carbon including graphite and 

 diamond. Those meteoric constituents found rarely if ever in terres- 

 trial rocks are the various alloys of nickel and iron, to which the 

 names Tcamacite, taenite, and plessite have been given; the nickel and 

 iron phosphide sclireihersite; the iron and chromium sulphide dau- 

 hreelite; the iron protochloride lawrencite; the calcium and titanium 

 or zirconium oxysulphide oshornite; the calcium-sodium phosphate 

 merrillite; the iron and nickel carbide cohenite; the carbon silicide 

 moissanite; an isotropic mineral believed to be a re-fused plagioclase 

 and called maskelynite; and a form of silica, asmanite. These are 

 described in some detail, in alphabetical order below. 



Apatite. — The phosphoric acid reported in the numerous analyses 

 of meteoric stones has in times past been considered a constituent 

 of the mineral apatite. As a matter of fact, crystals of this mineral 

 in a meteorite have been actually observed only by Berwerth, in the 

 stony portion of the Kodaikanal, India, siderolite. If occurring at 

 all, it is usually in the form of microscopic granules, though Lacroix 

 has recently described the mineral in the form of microscopic needles 

 in the metal of the Saint Sauveur stone. Late investigations have 

 shown that the prevalent phosphatic mineral is not a normal apatite, 

 but a new mineral^ — a calcium-sodium phosphate — differing in its 

 crystallographic and optical properties, and to which the name 

 merrillite has been applied.^ (See also p. 7.) 



Asmanite. — This name was proposed by Maskelyne ^ for a mineral 

 consisting essentially of silica, occurring in the meteorite of Brei ten- 

 bach, of which it composed nearly one-third of the siliceous portion. 

 The mineral, when pure, is colorless, with a specific gravity of 2.245, 

 a hardness of 5.5, and is rhombic in crystallization. It is commonly 

 believed to be identical with the tridymite of terrestrial rocks. 



Breunnerite. — This is the name given by Haidinger to a ferriferous 

 variety of magnesium carbonate occurring in terrestrial rocks and 

 in a single instance in a meteoric stone, that of Orgueil, France. It 

 is the only instance known of a carbonate compound occurring as an 

 original constituent of meteorites. Its original meteoric nature is 

 perhaps questionable. 



Carbon. — Carbon as the gas carbon monoxide (CO) or dioxide 

 (CO2), or in the amorphous and crystalline form of graphite has been 

 recognized as a constituent of certain meteorites, particularly meteoric 

 irons, for many years. Berzelius recognized a carbon compound in 

 the stone of Alais as early as 1838. Wohler and Cloez in 1839 found 



s Wherry, Edgar T., Amer. Mineralogist, vol. 2, no. 9, 1917. 

 ' Philos. Trans. Royal Soc, London, 1S71, p. 361. 



