576 HESS AND schaller: pintadoite and uvanite 



cements. The iron compounds in a cement are resistive to 

 hydration. Iron does not form crystalline hydration products, 

 but occurs as a rust-hke material. 



The initial set of cement .is affected by the action of small 

 amounts of electrolytes in retarding coagulation of the aluminate 

 material. With a limited amount of water, such as used in 

 normal consistency mixes, the aluminates coagulate and separate 

 from supersaturated solutions as amorphous bodies, the rate of 

 coagulation being affected by such small quantities of electro- 

 lyte as to nullify the possibility of the reaction being solely a 

 chemical one. 



Failure of cement in accelerated tests is due to the growth of 

 large lime hydrate crystals. The disrupting action results from 

 the pressure caused by growing crystals. Cements will fail in 

 the boiling test which contain lime sufficiently fine and high 

 burned, so that during boiling it hydrates and crystallizes. The 

 growth of crystals is siffficient to cause disintegration. When a 

 cement passes the boiling test but not the autoclave test, it 

 contains lime so coarse or high burned as not to hydrate in the 

 boiling test, but only in the autoclave, due to the high tempera- 

 ture and pressure employed. Some cements will pass either 

 test only after ageing. In this case aeration with insufficient 

 water to allow solution and crystallization causes the lime to 

 hydrate as amorphous hydrate, and in the accelerated tests 

 there is no crystallization and no disintegration. 



The reactions when cement is subjected to the autoclave 

 test are not abnormal. The disintegration action attributed to 

 the crystallization of the sulpho-aluminate has been greatly 

 exaggerated. 



MINERALOGY. — Pintadoite and uvanite, two new vanadium min- 

 erals from Utah: A preliminary note. Frank L. Hess and 

 Waldemar T. Schaller, Geological Survey. 



During an investigation in the fall of 1913 by Frank L. Hess 

 and B. S. Butler of that part of the central plateau uranium- 

 vanadium field which lies in Utah, a number of uranium and 

 vanadium minerals hitherto undescribed or little known were 



