40 ANNIVERSARY ADDRESS. 



green, and takes a good polish. In tin's condition it is often 

 traversed by veins of chrysolite, At Kanala the structure is 

 fibrous. In the north-west, at Koumac, it is sometimes yellow- 

 ish-grey, containing much chromatc of iron. Elsewhere it takes 

 the schistose structure, and recalls to mind the wliite argillaceous 

 schists which arc intimately associated with the scrpentinous 

 schists. 



A remarkable common character of the Serpentines is their 

 containing immense masses of red clay, derived from the decom- 

 position of the rock itself, when it contains Diallage in abund- 

 ance. In this case, in the midst of the argillaceous masses, there 

 are heaps of chromate of iron, also limonite, with diallage in 

 nests in different stages of decomposition. But the Serpentine 

 does not always end in clay ; sometimes both in the north and in 

 the south it loses its magnesia, presenting only a fibrous skeleton 

 of silica, which in certain instances passes into a green or white 

 Opal with dendrites ; the opal also becomes mammillated. The 

 fibrous skeleton passes sometimes into pulverulent silica with, 

 occasionally, carbonate of magnesia. 



Yery pure veins of hydro-silicate of magnesia, with a mammil- 

 lated structure, appearing as if precipitated, occur in the midst 

 of the Serpentines in the south of the island.. Monsieur Terreil 

 'analyzed this hydro-silicate at the Paris Museum, and found its 

 indications very near those of the Gymnite of Massachusetts. 



This rock, which is commonly yellowish blue, a little trans- 

 lucent, is elsewhere, e. y., at Kanala, strongly coloured green. 

 The colouring matter, after numerous and patient investigations 

 by Monsieur Jannettaz, appears due to a Silicate of nickel, 

 which, as we shall presently see, says Monsieur Gamier, is very 

 frequently represented in the midst of the eruptive magnesian 

 rocks. 



" In fact, the serpentines themselves are frequently covered 

 with a green coating, which is no other than this silicate 

 of nickel; the cavernous quartz which particularly at Koe, 

 abounds in the serpentinous formations, has the cells more or 

 less commonly filled with the silicate of nickel. 



