300 D. H. Browne — Phosphorus in Iron Mtn., Mich. 



black hematite, occurring in thin laminae, which cleave very 

 readily from each other in the direction of the strike. These 

 layers alternate in places with thin seams of calcinm-magnesium 

 carbonate. The ore analyzes from 65 to 68 per cent in iron, 

 in silica from 1 to 4 per cent, and in phosphorus from "005 to 

 •200. The ore is separated into Bessemer and non-Bessemer ; 

 about one-half falling below *035 x3hosphorus ; the rest aver- 

 aging about '075. At first sight, the ore upon analysis, seemed 

 to have no regularity whatever in percentage of phosphorus. 

 A room as stopped up, would change from Bessemer ore to non- 

 Bessemer, or vice versa in a way at first totally inexplicable. 



The fact that phosphorus exists as calcium phosphate led me 

 to infer thafsome proportion between the percentage of lime 

 and phosphorus might be found to exist; but such inference 

 was not verified in practice. An ore containing 2 per cent of 

 lime may contain almost no phosphorus, or may run high above 

 Bessemer limit. ISTor was any proportion manifest between the 

 percentages of iron or silica and phosphorus. I have noticed 

 jasper vary as much in percentage of phosphorus as any iron 

 ore, and similarly a lean ore is just as likely to be Bessemer as 

 non-Bessemer. The only difference I could find between 

 Bessemer and non-Bessemer was this : As a rule a soft blue 

 hematite high in phosphorus, has a brighter and more specular 

 appearance than non-Bessemer ore of the same value in iron. 

 This distinction, slight as it is, will not always hold good, and 

 the separation of such ores must be guided solely by chemical 

 analysis. 



The fact that a bright ore was high in phosphorus, and that 

 such ore was generally found near the hanging wall led me to 

 search for some regularity of phosphorus distribution, depen- 

 dent upon the position of the ore. After making analysis of 

 the ore from any room, drift or winze, I marked the percent- 

 age of phosphorus in a map of that portion of the mine. Hav- 

 ing thus obtained a chemical map of each room, I noticed in 

 each a certain regularity which seemed to me to throw con- 

 siderable light both upon this problem of phosphorus distri- 

 bution, and upon the vexed question of the method of formation 

 of the hematite ore deposits. 



In order to give a clear idea of this relation I must first state 

 a few facts with regard to the physical features of the deposit. 

 As previously stated, the so-called "veins" of the Ludington 

 mine stand nearly vertical, dipping north and pitching west. A 

 horizontal cross section of the ore-body shows it to form an 

 elongated lens about 65 feet in thickness at the center, ta- 

 pering to an acute point at both ends (fig. 1). A vertical cross 

 section shows the dip to the north, and also the fact that the 

 hanging wall is more curved than the foot. A cross section of 

 the Chapin Mine, which possesses the same physical features, 



