1908\ 
Monazite and Monazite Mining 
75 
taining considerable quartz debris and fragments of other light 
colored rocks, such as pegmatite, granite, mica, and cyanite gneiss. 
On the other hand, the absence of much quartz and pegmatitie or 
granitic debris from the gravel is generally characteristic of low 
grade deposits of monazite. The presence of black sands — mag- 
netite, ilmenite, hornblends, etc. — in the gravels does not neces- 
sarily indicate a low grade deposit, unless quartz and pegmatitie 
minerals are also lacking. Monazite deposits in regions where 
hornblende rocks are abundant generally contain a large percent- 
age of black sands, and it is then often difficult to concentrate 
the monazite to a marketable grade. As an offset to this, how- 
ever, especially in regions where granite is associated with the 
hornblendic rocks, gold is often found in the concentrates in quan- 
tity more than sufficient to pay the cost of separation, and in the 
same localities the concentrates generally carry also a quantity of 
zircon. This zircon is in the form of small, clear crystals with 
brilliant lustre, which range in size up to 1 millimeter square and 
about 2 millimeters long. 
Residual Deposits 
It has been found profitable to sluice down and concentrate the 
surface soils on the lands adjoining some of the richer monazite 
bearing deposits. The residual soils that have suffered but little 
displacement on the surface can be thus profitably washed to a 
depth of 3 or 4 inches, and where the drift soil has collected on 
the gentle slopes below a steeper hillside several feet can be sluiced 
down in some cases. The partial concentration of monazite in the 
top layer of soil is caused by the washing away of the clay and 
other light decomposition products of the rock. The supply of mon- 
azite in the stream gravels in favorable areas is often replenished 
by the wash from the hillside soils during rains; especially where 
the hills have any considerable slope and the land is cultivated. 
Under such conditions the stream gravels are often worked two 
or more times in a year. 
The saprolite or rotted rock underlying the richer deposits of 
monazite is at some places sluiced down to depths of a few inches 
to a foot or so, along with the overling gravels. At other places 
small amounts are removed and washed separately for the mona- 
