792 MINERALOGICAL DESCRIPTION OF THE ISLAND OF EANKA. 
on the surface, often approaching to hotryoidal and in all instances 
bearing strong marks of attrition. It exhibits many excavations 
and cellulosities which, appearing on the surface, occasion the irre¬ 
gular form, but the fracture of the interstices is uniformly coloured 
and compact. The surface sometimes indicates a mixture of red 
and black Iron-stone. 
2. Fragments of sand-stone of different colours and consistence. 
3. Fragments of quartz and felspar united to masses of various 
admixture from decomposed granite. 
4. Small fragments of granite. 
5. Small fragments of Black-Iron-stone. 
The last point of the large depository of Iron which I examined 
was on the summit of the alluvial ridge to the north of Minto, above 
the western extremity of the village : on the track hither from the 
settlement, along the elevated parts of the ridge, I passed over se¬ 
veral veins of Red-Iron-stone and Poudingues which will he men¬ 
tioned in the enumeration of substances found on the ridge. 
The depository consists here of an immense bed or accumulation 
of Argillaceous Iron ore, appearing uniformly of that species which 
is called Nodular Iron-stone, Aetitis, Eagle-stone or Geodes. That 
portion of the surface which was exposed to view, and which I ex¬ 
amined, was about 50 yards square and completely covered with 
Geodes. A ditch had been cut along one of the sides to the depth 
of 10 feet, extending exclusively through the same bed. The spot 
had been intended for a fort many years ago by the Sultans of PJem- 
bang, and was distinguished by the name of Renting Saribu. It 
had lately served for the dwelling of the noted exile Radio Japhar, 
who had more completely cleared it and opened the ditch; it ex¬ 
tended furthest in a direction north and south, and, where I exa¬ 
mined it, penetrated exclusively through this accumulation or bed 
of Geodes, whose extent is probably much greater than the exposed 
surface, but which it was not in my power to trace in its full extent. 
The separate nodules are imposed upon each other with a small 
quantity of intervening earth* Their size is various, from a diame¬ 
ter of nearly three inches to that of less than one inch. They have 
uniformly a disposition to a polyhedrons figure ; in many cases several 
of the sides are completely regular and defined. The surface is 
smooth, inclining to glossy or marked with pits and excavations. 
Some of the nodules are almost completely regular. I liav.e one 
specimen in which the two shorter sides forming a trapezium are re- 
