'215 



They are dense, of a whitish grey colour, and contain specimens of 

 Globigerina, so that they are perhaps of equal age as similar rocks 

 that are found likewise in islands to the North of New Guinea, and 

 according to Rutten are not younger than old-miocene '). 



The most important rock of the island is however formed b}' the 

 above-mentioned ±16 m. high phantastic rocks, some of whicii are 

 likewise found isolated in the neighbourhood of the eastern shore. 

 This rock, hitherto unknown in the Dutch East Indies, is a phosphorite 

 which shows great resemblance to the phosphates of other islands 

 of the Pacific. It is of a yellow lo reddish-brown colour and some- 

 times of a pitchlike appearance. Angular, yellowish-white parts give 

 to the rock a brecciated character. The specific weight amounts to 

 2.78 and the hardness is ;= 6. 



In thin sections the rock lias under the microscope the appearance 

 of a light-yellowish, structureless mass, intersected with fine and 

 irregular fissures. Some parts of the thin sections are rather opaque, 

 but everywhere dispersed ai'e dark dots which are apparently of 

 an organic origin. Though amorphous the phosphorite shows a slight 

 double-refraction, in which the interference-colours do not surpass 

 the iron-grey of tlie first order. In some parts one discovers through 

 the phosphate cavities filled up in zones that remind entirely of 

 the formation of agates (fig. 1), u |)henomenon that is quite common 

 in phosphates from the Pacific'). 



Fig. ]. 



1) 1. c. p. 29—31. 



2) Carl Elschnee. Gorallogene Phosphat-Inseln Austral-Oceaniens und ihre 

 Produkle. Liibeck 1^*13, p. 5.^, pi. I fa. Such like phosphale-agates are found in 

 the Isle of Nauru itself in rather large pieces (1. c. p). Vlllb). 



15* 



