No. 4.1 RESEARCHES ON METEORITES— MERRILL. 5 



should bo stated that a particle tested by the immersion method showed an index of refraction 

 of 1.625. Far more abundant than the phosphate is a limpid, colorless mineral, likewise occur- 

 ring interstitially, but locally so abimdant as to form almost the base in which the other silicates 

 are embedded. The mode of occurrence and appearance are in every way characteristic of the 

 so-called maskolynite, but that in many instances the area between crossed nicols breaks up 

 into granular aggregates which are plainly biaxial and give distinct polarizations in light and 

 dark, rarely yellowish colors in the thicker sections. The dark cloud, as a rule, sweeps over the 

 face of the crystal in a manner indicating conditions of strain, and in no case have I been able 

 to find a satisfactory section showmg the emergence of an optic axis, or other indications of its 

 optical properties than the indistinct black brushes sweeping across it as the stage is revolved. 

 It is apparently positive. There are no signs of cleavage, but in a few instances faint lines 

 were observed traversing the section. In these cases I was able to measure extinction angles 

 against these lines, of 8° and 10°. But for its very evident doubly refracting properties the 

 mineral woiild have been set down at once as maskelynite. As it was, additional tests seemed 

 necessary. Two determinations of its refractive index by the immersion method gave 1.54 

 and 1.545, which is higher than that of a similar appearing mineral to which I have frequently 

 referred in other publications. All further doubts as to the nature of the substance are, how- 

 ever, in this particular case set at rest by the finding of occasional granules still retaining 

 residual traces of the characteristic twinning bands of a plagioclase feldspar. 



Homestead, Iowa. — The Homestead meteoric stone fell on February 12, 1875, and is now 

 represented by 124,492 grams scattered among 62 collections throughout the world. It has 

 been the subject of numerous papers, concerning which a reference to Wiilfing's bibliography is 

 here sufficient. The stone is classed by Brezina as a brecciated gray chondrite (Ccb), and by 

 Meimier as a limericldte. Wadsworth, who examined the stone in tliin section, states it to 

 consist of "crystals and grains of ohvine, enstatite, pyrrhotite, iron, and base," and quotes 

 Lasaulx as stating that it carries plagioclase. Several chemical analyses have been made, 

 none of which show the presence of any unusual constituents. This is little to be wondered at 

 when one considers that in the case of Gumbel but 1.5 grams of material were at his disposal. 

 Much of the interest that is attached to the stone is due to A. W. Wright's work on the gaseous 

 contents of meteorites. 



My own attention was firet drawn to this stone when studying the occurrence of the cal- 

 cium phosphate concerning which I have of late written several papere, and which, inciden- 

 tally, I find here in abundant characteristic forms. I do not find the plagioclase feldspar 

 referred to by Lasaulx, but do fimd in some of the chondrules a polysyn- 

 thetically t^vinned monoclinic pyroxene which seems to have been wholly 

 overlooked by previous observer's. The immediate cause of the present 

 note is, however, the occurrence in each of two shdes examined of a minute, 

 bright red-brown, scarcely translucent, isotropic mineral embedded in ensta- 

 tite, as shown in the drawing reproduced here. (Fig. 2.) An attempt at a 

 definite determination of its mineral nature was a partial failure. Finding it 

 insoluble in ordinary acids, one of the slides was sacrificed, painting aroimd 

 the object as closely as possible with vaseline and then covering the exposed 

 portion with a large drop of fluorhydric acid. The siUcates were all decom- 

 posed badly, but amidst the gelatinous mass of decomposition products I 

 was still able to detect the red granule apparently untouched. In an attempt to remove the 

 granule for further tests and observation, it became hopelessly lost. I can only surmise from 

 its apparent insolubihty, subtranslucency, color, isotropic nature, and a suggestion of octahe- 

 dral form, that it may be a spinel. That it is osbomite does not seem probable. The second 

 slide, from which the accompanying figure was drawn, has been covered and preserved. I may 

 add that eight other small sections, cut from fragments of the stone in the Barker bequest, gave 

 no new occurrences of the mineral. This is probably the same mineral noted by Gumbel ' but 

 thought to be garnet. The decidedly octahedral termination on the form figured in the present 

 paper seems to warrant its being considered a spinel. 



> Sitz. der Uatt-phys. Classe, der K. bayriscben Akad. tu MOncben Dec. 1875, p. 323. 



