82 WATSON AND GOOCH: VIVIANITE from FLORIDA 



The final mean is 0.9320 ampere, and the average deviation 

 is 0.18 per cent. The final mean, neglecting the readings of 

 one observer, is 0.9330 ampere, and the average deviation is 

 0.06 per cent. Thus this method can be used to define a 

 standard current with an accuracy of 0.2 per cent. 



It may be pointed out that both of the above methods give 

 results that are practically independent of the temperature of 

 the room. Hence, an ammeter designed on these principles has 

 a zero temperature coefficient. ' 



* 



MINERALOGY. — Vivianite from the land pebble phosphate de- 

 posits of Florida. Thomas L. Watson and Stapleton D. 

 GoocH, University of Virginia. 



introduction 



During recent mining operations by the Coronet Phosphate 

 Company on its property on the Northwest Quarter of Section 

 34, Township 29, Range 22, about If miles southeast of Plant 

 City, Florida, fairly abundant crystals of vivianite were exposed 

 over an area of moderate dimensions. The occurrence was noted 

 by the junior writer, who is chemist to the Coronet Phosphate 

 Company, and who kindly sent the senior writer a liberal supply 

 of the mineral and matrix for study. 



Although not a common mineral, vivianite has been observed 

 both in this country and abroad in a variety of associations, 

 more especially in veins with the sulphides pyrite and pyrrho- 

 tite, in bog iron ore deposits, and in clays and marls. In all its 

 occurrences the mineral is regarded as secondary in origin. 



Previous to the recent mining operations by the Coronet 

 Phosphate Company near Plant City that resulted in exposing 

 vivianite, the only reference to the occurrence of the mineral in 

 Florida phosphate deposits found in the literature accessible to 

 us is a general statement by Matson,i who remarks that vivian- 

 ite has been noted at several places but is probably rare. In a 



1 Matson, G. C. The phosphate deposits of Florida. U. S. Geol. Survey 

 Bull. 604, p. 85. 1915. 



