tgneous rock 
65 
of the cave are lined with an oxide of manganese incrustation, and on the 
floor is a deposit of cave dust that may contain interesting remains of the 
indigenous fauna. Lying on the floor, when discovered, were the skeletons 
of several foxes. The costean has been excavated to a depth of 21 feet at 
the deepest part, and the floor of the excavation is all on Heathcote rocks, 
except for a width of about 8 feet in the centre of the costean, where limonite 
still goes down. Probably a few feet more m depth would cut this out also. 
Loose bLocks 
Limonite 
A/ an of S Floor of Costean 
Fig. 28.— Section of No. 2 Costean. Scale, 20 feet to 1 inch. 
In No. 2 costean, at the surface limonite is exposed for a width of over 
70 feet; but at a depth of less than 10 feet, in the floor of the costean, 
tongues of the limonite ore are showing that together only amount to 19 feet 
along the line of section. 
Iron ore has replaced the stratified rocks by metasomatic action, and 
this is the result of atmospheric influences ; consequently, the ore has 
accumulated only at and near the surface. 
There are some thousands of tons of limonite at the surface that could 
be quarried out, but it does not extend downwards. It is not a lode of the 
usual character, but merely the exposed edges of certain very ferruginous 
beds that have been altered into limonite and manganese ore by replacement. 
Assays of the limonite made at the Geological Survey Laboratory are as 
follows :— 
Per cent. 
From No. 1 costean— 
No. 13.—Iron .. .. .. .. 47 *87 
No. 45.—Iron .. .. .. .. 46’23 
No. 59.—Iron .. .. .. .. 47*24 
No. 149.—Iron .. .. .. .. 39*28 
Manganese .. .. .. 12 *42 
From No. 2 costean— 
No. 14.—Iron .. .. .. .. 45*92 
No. 46.—Iron .. .. .. .. 48*75 
No. 60.—Iron .. .. .. 35 *32 
No. 150.—Iron .. .. .. 36 *03 
Manganese .. .. .. 16 *76 
A sample of greenish clayey material (chloropal) from No. 1 costean gave 
on partial analysis :— 
Per cent. 
Silica .. .. .. .. 47 *8 
Iron and alumina .. .. .. 30*7 
Lime .. .. .. .. .. nil 
Magnesia .. .. .. .. 1 *3 
Water .. .. .. .. 19 *0 
98*8 
6318.—3 
[11.4.12.] 
