Geiith.J 400 [August IS. 



Associated with the yelh)w grains are small crystals of a dark brown 

 almost black tourmaline, small crystalline plates of menaccanite and color- 

 less or slightly yellowish and brownish-white zircons, the latter more or 

 less water-worn, but showing the planes of the prism I, the pyramid 1 and 

 also less distinct, the planes of the pyramids ii, and 33. 



As it is an impossibility to pick out enough of the pure yellow grains 

 for analysis, I made several unsuccessful attempts to analyze the mixture, 

 and obtained by Pisani's method 79.07% of titanic oxide. 



I had, at the expense of one week's labor, picked out a little over two 

 milligrams of perfectly pure yellow grams, which Dr. G. A. Koenig had 

 the kindness to test by his colorimetric method, and pronounced to be 

 almost pure titanic oxide, the yellow grains are therefore probably a va- 

 riety of rutile. 



In the rock itself the yellow grains show the same sharp angular forms 

 above mentioned, whilst the zircons are water-worn. It appears from 

 this that the rutile, tourmaline, mica and menaccanite crystallized or rather 

 separated when or after the itacolumite was deposited, whilst the zircons, 

 together with the quartz, are remnants of decomposed rocks, probably com- 

 ing from granulites. In those of the South mountains, I have frequently 

 observed microscopic zircons, very similar in form to those in the Edge 

 Hill rocks. I maj^ mention that Prof. Zirkel (Jahrb. f. Mineralogie, 1876, 

 00), has also detected microscopic zircons in the granulites of Saxony. 



Artificial Rutile and Octahedritc. 



Whilst decomposing some of the mixed yellow sands, containing about 

 80 % of rutile, by fusion with a rather small quantity of potassium hydro- 

 gen sulphate, I was interrupted in my work for several hours, so that the 

 greater portion of the potassium hydrogen sulphate was converted into 

 potassium sulphate. By dissolving in cold water most of the titanic oxide 

 w.^nt into solution, but I noticed a pale brownish, heavy, sandy substance, 

 which, under the microscope, appeared in very brilliant crystals of the 

 usual form of rutile /and ii, and pyramids 1 and li. One or two of the 

 crystals Avere twins. There were, perhaps, several hundred of rutile 

 crystals. Amongst these I observed two crystals of octaliedrite which had 

 the acute pyramid 1 and a decided blue color. 



Experiments which I subsequently made for the purpose of making 

 these artificial rutile crystals from pure titanic oxide were not very 

 successful ; although I have repeatedly obtained microscopic quadratic 

 forms, I never could get any distinct brilliant crystals. 



VII. Sphalerite and Pi'ehnite, from Cornwall, Lebanon Co.. Pa. 

 a. Sphalerite. 



About two years ago small crystals of a greenish mineral were discov- 

 ered by 3Ir. E. E. Craumer, of Lebanon, Pa., associated with a white 

 crystalline coating upon the magnetite of the great Cornwall Ore Bank. 



