10 



BULLETIN 149, UNITED STATES NATIONAL MUSEUM 



Oldhamite. — This name was given by Story-Maskelyne, in 1862, to 

 a calcium sulphide (CaS) found by him in the meteorite of Busti 

 and described in detail in the Philosophical Transactions of the Royal 

 Society of London for 1870. The mineral is of a pale, chestnut brown 

 color when pure, though often covered on the outer surface by a 

 gypseous oxidation product. It occurs in the form of rounded 

 granules, with cleavages essentially rectangular, imbedded in the 

 pyroxenic constituents. It is optically isotropic and is considered to 

 belong to the cubic or isometric system. Specific gravity 2.58. 

 Boiled in water it is decomposed, yielding a bright yellow solution of 

 calcium polj^sulphide and an insoluble residue. It readily undergoes 

 alteration into gypsum, hydrous calcium sulphate, which probably 

 accounts for its apparent rarity. As gypsum is itself readily soluble, 

 its possible presence may be determined by boiling the powdered 

 stone in water and then testing the solution for calcium and sulphur. 



Olivine. — ^A magnesium and iron silicate of the formula (MgFe) 

 Si02; relative proportions of magnesia and iron are, however, some- 

 what variable, as shown in the following analyses.^* 



Locality 



SiOj 



MgO 



FeO 



1. Krasnojarsk, Siberia 



2. Kiowa County, Kansas 



3. Brahin, Russia 



4. Atacama, Chile 



40.24 

 40.70 

 39.61 

 36.92 



47.41 

 48.02 

 48.29 

 43.16 



11.80 

 10.79 

 11.88 

 17.21 



The mineral rarely occurs in good crystal form except in the 

 porphyritic chondrules, though in the pallasites of Krasnojarsk 

 and Lodran, blebs with determinable crystal faces have been found. 

 It is of all meteoric minerals perhaps the most abundant and wide- 

 spread, sometimes, as in those of Warrenton, Mo., and Chassigny, 

 France, composing a very large proportion (75 per cent) of the mass 

 of stone. It is rarely, if ever, wholly absent, even the iron meteorites 

 showing in most cases included granules. It is also a common and 

 widespread constituent of terrestrial igneous rocks. Its appearance 

 is easily determinable by the unaided eye in the pallasites and its 

 meteoric characteristics shown in the illustrations of chondritic 

 structures (pis. 22 and 23). The statement frequently made— first 

 I believe by Daubree — -to the effect that meteoric olivines differ from 

 their terrestrial prototj^pe in containing no nickel, needs confirmation. 

 Indeed many careful analyses could be quoted showing the direct 

 opposite. 



Oshornite. — This name is also one of Maskelyne's proposal. The 

 mineral occurs in golden yellow microscopic octahedra associated 

 with the oldhamite in the Busti meteorite only, so far as now known. 



'* Tscherwinsky gives the average composition of the olivine of pallasites as follows: SiOj, 39.35; FeO , 

 14.39; MgO, 45.93; MnO, 0.08; NiO, 0.02; CaO, 0.03; NajO, 0.02; AljOs, 0.09; YeiOi, 0.06; Sp. Gr. 3.38. 



