224 



KEPORT OF NATIONAL MUSEUM, 1899. 



analyses by Dr. J. Lawrence Smith, from whose papers on the subject 

 these notes are partiall}^ compiled: 



Geologicalh' emery, like corundum, belongs mainly to the older 

 crystalline rocks. In Asia Minor it occurs in angular or rounded 

 masses from the size of a pea to those of several tons weight, embedded 

 in a blue-gray or white crystalline limestone, which overlies micaceous 

 or hornl)lendic schists, gneisses, and granites. Superficial decompo- 

 sition has, as a rule, removed more or less of the more soluble portions 

 of the limestone, leaving the emery nodules in a red ferruginous soil. 

 With the emery are associated other aluminous minerals as mentioned 

 below. 



According to Tschermak^ the Naxos emery (Specimen No. 60465, 

 U.S.N.M.) occurs mostly in the form of an iron-gray, scaly to schistose, 

 rarely massive, aggregate consisting essentially of magnetite and corun- 

 dum, the latter mineral being in excess. In addition to these two 

 minerals occur hematite and limonite, as alteration products of the 

 magnetite; margarite, muscovite, biotite, tourmaline, chloritoid, dias- 

 pore, disthene, staurolite, and rutile occur as common accessories; 

 rarely are found spinel, vesuvianite, and py rite. Under the microscope 

 he finds the emery rock to show the corundum in rounded granules 

 and sometimes well-defined crystals with hexagonal outlines, particu- 

 larly in cases where single individuals are embedded in the iron ores. 

 (Plate 9, fig. 3.) In many cases, as in the emery of Krenino and 

 Pesulas, the gran .les are partially colored blue by a pigment some- 

 times irregularly and sometimes zonally distributed. The corundum 

 grains, which vary in size between 0.05 mm. and 0.52 mm. (averaging 

 about 0.22 mm.), are very rich in inclosures of the iron ores, largely 

 magnetite in the form of small, rounded granules. The quantity of 

 these is so great as at times to render the mineral quite opaque, though 

 at times of such dust-like fineness as to be translucent and of a brownish 



^Mineralogische und Petrographische Mittheilungen, XIV, 1894, p. 313. 



