K. 8. Hoiuard — Elm Creek Aerolite. 381 



fragments and splinters and in chondrules of the barred and 

 porphyrinic type common to meteorites. A part of the por- 

 phyritic forms show a base of yellowish glass, while others 

 seem holocrystalline. Occasional forms are met with in which 

 the entire chondrule is composed of a single individual, in 

 which case the central portion is clear and colorless, while the 

 borders are of a light smoky-brown color and show a fibrous 

 structure. All portions are, however, optically a unit. 



" The enstatiteslike the olivines occur in scattered fragmental 

 particles and in chondrules, the latter of the common crypto- 

 crystalline and radiate type, and in porphyritic forms. In the 

 latter the crystal outlines are at times very well developed. 

 The cryptocrystalline forms are often remarkably spherical, or 

 at least circular in outline in the section. As such they rarely 

 polarize as a single individual, but as is commonly the case 

 the field breaks up into sectors, as the stage is revolved between 

 crossed Nicols. It is of course possible that not all of these 

 cryptocrystalline forms are of enstatite ; some may be of 

 augite or possibly olivine. An optical determination is impos- 

 sible, and the determination is based on their resemblance to 

 others which have been tested chemically. 



"The monoclinic pyroxene is of interest on account of the 

 beautifully developed polysynthetic twinning which it presents 

 when either in chondrules or in fragments in the groundmass. 

 In this respect it would seem to be fully comparable with the 

 meteorite of Renazzo, Italy, as figured by Tschermak on Plate 

 15 of his Mikroskopische Beschaffenheit der Meteoriten. 

 Crystal outlines are rare and the mineral is a trifle less limpid 

 than the enstatite. A prismatic cleavage is fairly well devel- 

 oped. No feldspars or other silicates than those mentioned 

 were detected. 



" The most striking feature of the stone is the spherical per- 

 fection of many of the chondrules and the perfection of the 

 twinning in the pyroxene. As a whole the stone is plainly 

 fragmental — is composed of a moderately firm mass of angular 

 fragments in which are imbedded the chondrules. I am dis- 

 j)Osed to class it with those of Allegan, Michigan, San Emig- 

 dio, California, and Warrenton, Missouri. ' This, following 

 Brezina, would throw it in the group of Ornansite (CcO), from 

 which it differs only in its firm character. I confess, however, 

 that I fail to see the necessity of attempting to name rocks 

 according to their degree of compactness or friability." 



