46 JOURNAL OF THE 



here in commercial quantities was £rst established in 

 1887. The thickness of these stream g; ravel deposits 

 is from one to two feet. The percentage of monazite 

 in the original sand is very variable, from an infinites- 

 imal quantity to one or two per cent. 



WASHING AND CLEANING MONA^ITE SAND. 



The monazite is won by washing- the material in sluice 

 boxes, about 8 feet long- by 20 inches wide by 20 inches 

 deep, exactly after the manner that placer gold is 

 worked. Magnetite, if present, is eliminated from the 

 dried, concentrated sand by treatment with a large 

 hand magnet. Many of the heavy minerals such as 

 zircon, menaccanite, rutile, brookite, corundum, g"ar- 

 net, etc., cannot at present be completely separated. 

 The commercially prepared sand, therefore, is not pure 

 monazite. A cleaned sand, containing from 65 to 70 

 per cent, monazite is considered of good quality. 



The most systematic washing method employed is 

 by the use of two sluice boxes, the mouth of one dis- 

 charging into the head of the other, placed below. The 

 gravel is charged on a perforated plate at the head of 

 the upper box, and the clean up is so thoroughly washed 

 as to g-ive a high grade sand, often up to 85 per cent, 

 pure. The tailings discharge directl}^ into the lower 

 box, where they are rewashed, producing a second 

 grade sand. At times the material is siibjected to as 

 many as five similar consecutive washing- treatments in 

 the sluice boxes. A further concentration of the dried 

 washed sand is sometimes made b_v pouring from a cup 

 in a line, steady stream from a height of about 4 feet, 

 on to a level platform; the lighter quartz and black 

 sand, with the line grains of monazite (tailings) fall on 

 the perijohery of the conical pile and are constantly 

 brushed aside with hand brushes; these tailings are 



