COMPOSITION AND STRUCTURE OF METEORITES / 



material. Two stony irons had an average of 6.88 by 10~^^ gram, 

 while of the seven irons examined but two were sufficiently active 

 for determination, the Toluca iron yielding 2.13 by 10~'^ grams, and 

 that of Coahuila 7.69 by IQ-^l 



Lawrencite. — Ferrous chloride. The exudation of drops of ferrous 

 chloride from freshly cut or broken surfaces of meteoric iron was 

 early noted, but it was not until 1855 that J. Lawrence Smith found 

 the material in the condition of a soft solid of a green-brown color in 

 the meteoric iron of Tazewell County, Tenn.^* In 1877 ^^ he also 

 noted the occurrence of the substance in the iron of Rockingham 

 County, N. C. In this same year Daubree thought to note its occur- 

 rence in the terrestrial iron of Ovifak, Greenland,'® and proposed for 

 it the name lawrencite in honor of its first discoverer. The material 

 liquefies on exposure to the atmosphere, the iron passing over quickly 

 to the condition of sesquioxide. It is to this mineral that is due the 

 "sweating" and rapid disintegration of so many irons, and causes 

 the stone meteorites to become rust-brown or freckled with rust- 

 colored spots. 



Merrillite. — This mineral, as a common but minor constituent of 

 stony meteorites, was first noted and described by Merrill in 1915 '^ 

 and the name proposed by Dr. E. T. Wherry in 1917.'^ Subsequent 

 more detailed investigations by Larsen and Shannon '^ have shown 

 it to be an entirely new compound of calcium, sodium, and phos- 

 phorus with the formula 3CaO, Na20, P2O3. 



Inasmuch as a description of this mineral is not to be found in the 

 literature in general, it may be given here in fuU. Occurrence spo- 

 radic, without crystal form, colorless and very brittle; cleavage for 

 the most part lacking, though sometimes imperfect and interrupted 

 showing angles of 60° and 120°. Optically uniaxial and negative; ^° 

 birefringence weak, less than 0.005; indices of refraction co = 1.626, 

 c = 1.620; specific gravity 3.10. (See pi. 3, fig. 2.) 



Metallic constituents; nicJcel-iron alloys. — These are essentially the 

 same in all meteorites. They occur in varying proportions from a 

 fraction of 1 per cent, as in the Bishopville stone, to upward of 90 

 per cent, as in the so-called iron varieties. In the stones the form 

 is that of disconnected drops or stringers; in the pallasites that of a 

 more or less disconnected mesh or sponge enfolding silicate minerals; 

 and in the metallic forms constituting nearly the entire mass. 



'< Amer. Journ. Sci., vol. 19, 1855, p. 154. 



i» Idem, vol. 13, 1877, p. 214. 



'6 Compt. Rend., vol. 84, 1877, p. CO. 



" Proc. Nat. Acad. Sci., vol. 1, 1915, p. 302. 



" Amer. Mineralogist, vol. 2, No. 9, 1917, p. 119. 



>» Amer. Journ. Sci., vol. 9, March, 1925, pp. 250-260. 



^ Wrongly given as biaxial and positive in first publication. Amer. Journ. Sci., vol. 43, 1917, p. 324. 



