NIAGARA FALLS AND VICINITY IO9 



amber crystals of calcite, were also found in these cavities, the com- 

 bination being such as to produce specimens of great beauty. 

 Among the rarer minerals found in this rock is the crystallized and 

 cleavable anhydrite, which like gypsum is a sulfate of calcium, but 

 without the water which is characteristic of that mineral. Anhydrite 

 crystallizes in the orthorhombic system, and its cleavage is in three 

 directions, at right angles to each other (pinacoidal), thus yielding 

 rectangular fragments and enabling one to distinguish it from 

 selenite with little difficulty. It is also a trifle harder than selenite 

 which is easily scratched with the finger nail. This form of anhy- 

 drite is rather rare, the principal localities for it being foreign. 

 Masses of considerable size have been found in the limestone of this 

 quarry, and small pieces are not uncommon in the geodes of these 

 strata. Both selenite and the cleavable anhydrite are commonly 

 called "mica" by the uninitiated; that mineral however does not 

 occur at Xiagara. Small masses of fibrous gypsum or satin spar 

 have been found, but these are very rare. The satin spar of which 

 the cheap jewelry sold in. the curiosity shops is made is not from 

 Xiagara. 



Among the metallic minerals found in this rock, zinc blende or 

 sphalerite is most common. It is generally of a yellowish or light 

 brownish color and brilliant resinous luster. Large masses how- 

 ever are rare. Galenite or lead sulfid crystals are also occasionally 

 found, but this mineral is comparatively rare. In addition to these, 

 iron pyrite, iron-copper pyrite (chalcopyrite), green copper carbonate 

 (malachite), fluor spar (nuorite), iron carbonate or brown spar 

 (siderite, generally ferruginous dolomite), strontium sulfate (celes- 

 tite) and native sulfur as well as other minerals are met with. 



The total thickness of the limestone exposed in this section is 

 thus somewhat more than 55 feet. At Lewiston hights, on the edge 

 of the escarpment, only about 20 feet are exposed. This includes 

 the two lower strata of hydraulic limestone, the crinoidal limestone 

 and a few feet of the lowest geodiferous beds (stratum 4). Over 

 this lie some two or three feet of glacial till. The distance between 

 the edge of the escarpment and the quarry at the end of the section, 

 is a little over a mile and a half, the increase in thickness of the 



