68 SUEVEY OF COLORADO AND NEW MEXICO. 



stratification. In tlie yalley of anotlier brancli of the Gallisteo, tliere is 

 a dike 'two feet wide witli the strike a little east of south. The clays on 

 each side are metamorphosed into slates. 



At another locality there is a bed of coal, which has been changed by 

 an enormous dike into anthracite. Section 1st, clay-slate ; 2d, two and a 

 half to three feet anthracite ; 3d, fourteen to eighteen inches of clay 5 4th, 

 fourteen inches to two feet of anthracite ; 5th, clay shale, i)assing up into 

 alternate layers of sandstone and clay, ten feet ; 6th, dark sandstone. 

 The dip of all the beds is fourteen degrees east. They are overlaid by 

 a thick bed of columnar basalt. The dike that covers the coal bed 

 trends about north and south, or a little east of south. 



The influences of ihe Cerillos on the north side of the Gallisteo, and the 

 Placiere Mountains on the south, lias produced a beautiful synclinal, 

 while the Cerillos form a sort of imperfect quaquaversal. The beds 

 dip from two sides of this small range at least, and the indications in 

 the channels of the little streams are, that the sandstones of the Gallisteo 

 group dip from a third side, but are now mostly concealed. We have, 

 therefore, in the valley of the Eio Grande, if my investigations are cor- 

 rect, three groups of tertiary beds of different ages. 1st. The coal strata, 

 with abnndant impressions of deciduous leaves, lying above well-marked 

 cretaceous beds. 2d. The Gallisteo sand group, which plainly overlies 

 the coal strata, but inclines equally mth and conforms to them. 3d. The 

 Santa Fe marls, which are of much later date than either of the other 

 two, and rest unconformably upon the Gallisteo g'roup, and never incline 

 ijiore than five or ten degrees. 



Although the coal beds lie high up on the sides of the Placiere Mount- 

 ains, I am inclined to the belief that some portions of the cretaceous 

 strata, and possibly even older rocks, are revealed on the sides of the 

 gneissic nucleus. This mountain seems to be penetrated with dikes, 

 which have given a dark somber hue to all the rocks. 



The mountain itself is very rich in minerals, as gold and iron ore. 

 Tlie Ortiz mine is the most celebrated, although a number of lodes have 

 been oi)ened. Colonel Anderson, formerly of the United States Army, 

 is superintendent of the mining interests of this region, and he has 

 already erected a forty-stamp mill, the most substantial one I have seen 

 in the West. The Ortiz lode is a very irregular one. It expands some- 

 times twelve feet or more, and then nearly closes up. It has yielded 

 very rich ore at times; mingled with this ore are fluorspar, calcspar, 

 crystallized quartz, blue and green carbonates of copper, a little native 

 copper, and the sulphurets of iron and copper — the latter predominates 

 in the ore. 



The Brehm lode has a strike about northeast and southwest, and by it 

 1 suspect the dip of the gneissic rocks, on the north side of the mount- 

 ains, to be about northwest. The width of the lode is about three feet, 

 the inclination of the vein southeast forty-five degrees. 



The Placiere Mountain seems to be rich in gold, but the want of water 

 may prevent the mines from being wrought with great profit. The sur- 

 face of the country is literally covered with i^lacer diggings, where the 

 drift g'old has been taken out by the Mexicans in old times by melting 

 snow. Magnetic iron ore seems to be abundant, and in the clays con- 

 nected wath the coal beds there is the largest supply of excellent brown 

 iron ore, so that the time is not far distant when iron works of great I 

 value may be erected in this region. 



