450 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Taking this analysis and the earlier ones, the mineralogical and chemical composition of the whole plate originally 

 investigated, after deducting carbonaceous particles and rust, may be reckoned as follows: 



III 



Kamacite 90. 511 



Angular pieces. 



Taenite G. 79 



Schreibersite and rhabdite 1. 73 



?»«■• 



100. 00 



IV IVa 



Fe 90.70 91.18 



Ni 8.41 8.22 



Co 61 .59 



Cu 01 .01 



P 27 



100. 00 100. 00 



The results under IVa show the composition after deduction of schreibersite. The 2.35 per cent of tamite obtained 

 by isolation after detucting 0.10 per cent for included nickel-iron phosphide totals only 34.61 per cent of the calculated 

 total result. 



Laspeyres 35 gave the following account of the detection of quartz and zircon in a specimen 

 of Toluca : 



The piece investigated was one of the largest of those collected by Krantz in 1S56 in the Toluca valley, and weighed 

 10,030 grams. It showed on the rusted surface many irregularly bounded earthy portions sometimes 50 mm. in length 

 and breadth, but always only a few millimeters thick, which at first glance resemble a very fine and somewhat loamy 

 sand cemented by rust. In this almost compact carpet are embedded numerous brilliant quartz crystals reaching a 

 size of 2 mm., as Rose has described. The earthy portions resemble many of the altered olivine nodules of meteorites 

 and basalts, except that the latter lack quartz. The quartz crystals, as Rose has described, can be easily separated 

 from the sandy matrix, but they can be more easily separated by dissolving the matrix in hydrochloric acid. They show 

 the forms: 



cc R (1010), R (1011), -R (0111). 



Like all silicates of meteorites this quartz is very fissile and brittle so that on scaling or loosening it easily falls into 



irregularly-bounded fragments. Measurements with the reflecting goniometer gave, for the unstriated rhombohedral 



faces, the following: 



Observed. Calculated. 



R (1011)-R (10TI)=46 o 5'-8' 45° 16' 



R (lOll)w R (10ll)=37° 44'-47' 38° 13' 



Neither with the lens nor under the microscope could any trace of a dulling or rolling of the corners or edges, or a 

 scratching of the faces, be observed. Under the microscope the crystal form appeared (as is common to the crystals of 

 meteoric irons, especially the well-known olivines in the Pallas irons) rounded on the corners and edges. The matrix 

 in which the quartz was embedded was treated with hydrochloric acid and a solution of sodium carbonate. Iron, 

 some clay, some magnesia, and silica were found in the solution. A very fine, seemingly sandy residue remained 

 which was embedded in Canada balsam. On investigation with the microscope this showed that it was not a sand 

 since there was no trace of erosion. The whole residue consisted of sharp cornered and edged grains, broadly prismatic 

 flakes, and sharply-formed crystals. Still more, the mineral composition of the residue forbade its being regarded 

 as a sand. The greater portion of the residue, about 60 per cent, consisted of colorless, transparent grains which belong 

 not only to quartz but also to plagioclase and perhaps also to orthoclase. The latter show, besides a good cleavage, 

 none of the twinning lamellfe which are so characteristic of plagioclase. They are also sharply bounded and in part also 

 crumpled, as in terrestrial rocks. Besides these completely colorless splinters occur single weakly reddish transparent 

 isotropic grains with traces of cleavage, more strongly refracting than quartz or glass and much weaker than the similarly 

 colored zircon. These grains I can only refer to garnet. Glass grains, such as were observed by Cohen and Weinschenk, 

 I could not find. The smaller portion, or 40 per cent, of the residue consisted of a brownish-green or green (though 

 according to the thickness now bright and now dark) mineral in the form of partly irregular and partly broadly prismatic 

 splinters with rectangular boundaries showing in their long dimension a very complete prismatic cleavage. The 

 extinction corresponds usually with the direction of cleavage and also shows pleocliroism in many of the lamellae. 

 Such belong, doubtless, to monoclinic augite, since in many pleochroitic splinters the extinction forms a sharp angle 

 with the cleavage direction, and hornblende has not yet been observed in meteorites. No cross sections could be 

 discovered. The most interesting constituent of the residue, however, was in the form of well-formed crystals rich in 

 faces from 0.04 to 0.15 mm. long and 0.02 to 0.07 mm. thick. These, from their form and optical characters, can be 

 nothing less than zircon, which has not been hitherto recognized in meteorites. The crystals are tetragonal and always 

 show the same forms, as follows: 



o (111), p (100), o' (101), q (110), d (m 11) 



