476 ir. K Hidden and J. B. Mackintosh — Yttria and 



noteworthy size and transparency, having been as yet found. 

 Small druses of quartz-caps are often met with in the seams of 

 the larger quartz masses. 



Hyalite, in mammillary forms was observed coating the 

 seams of the feldspar and quartz, in very small patches. 



Orthoclase, occurs massive and finely crystallized and in 

 great variety of form. Twin crystals, of curious complexity, 

 and simple forms are very common. Crystals of huge dimen- 

 sions, a foot or more in length, more or less perfect, and 

 smaller sizes abound, especially are they abundant on the con- 

 tact of the vein with the granitic walling. 



Albite is rare and occurs coating small cavities in the mas- 

 sive orthoclase. Crystals not above 1 inch diameter were ob- 

 served. 



Biotite (?), is very abundant and occurs in broad folia in the 

 seams between the quartz and feldspar masses. Diagonal pris- 

 matic cleavage surfaces were common. It was intimately 

 mixed with much magnetite and was often the matrix or 

 foundation upon which the rarer minerals rested. Many alte- 

 ration products were noticed. 



Muscovite is quite rare, and occurs as hexagonal implanted 

 prisms only in the albitic cavities. These prisms seem to be 

 made up of 3 or 6 sectors on a basal section. ]STo examination 

 chemical or optical has been made. 



Magnetite is quite abundant, both massive and crystallized. 

 It is always associated and intermixed with the biotite. Octa- 

 hedral crystals with planes of the cube, rhombic-dodecahedron 

 and of a trapezohedron were found abundantly, though super- 

 ficially they were coated with a thin micaceous layer and some 

 uranium hydrate. 



Martite was very common, being an alteration from the 

 magnetite. Crystals having a black color interiorly and pre- 

 serving the cleavages of magnetite but having no magnetic 

 properties were very commonly observed. 



Gadolinite. — We have already detailed the events sur- 

 rounding the discovery of this mineral in Texas. For a 

 description we would refer to the paper by Dr. Genth * in the 

 September number of this Journal. As Dr. Genth has stated, 

 this gadolinite when unaltered " has a black color ; in thin 

 splinters it is translucent with a dark bottle green color ; the 

 fine powder is greenish-gray ; fracture conchoidal to splintery. 

 Sp. grav. 4-201-4-254."f 



* Eakins found sp. g. = 4 - 239. Our own determination on a very compact 

 mass gave us 4*306. 



f Dr. Genth was misinformed by the party who supplied him with his 

 " Burnet Co. gadolinite " as it has not as yet been discovered in that county, and 

 the error of crediting Burnet Co. with having produced it was probably owing to 

 the fact that it had been shipped from Burnet (Burnet Co.) which was the nearest 

 R. R. point to the true locality some 19 miles distant.] 



