294 On the Artificial Formation of Minerals. 
corresponding therefore closely with Ramelsberg’s calcula- 
tion for apatite. 
The crystals obtained were too small for measurement, 
which the author considers sufficiently accounted for by the 
artificial conditions of their production. By examination, 
with the aid of the microscope, they were found to be six- 
sided prisms with terminal planes, and grooved lateral planes 
like beryl. In other respects they had the closest resem- 
blance to the acicular crystals of apatite, occurring in rocks at 
Capo di Bove. 
The density of this artificial apatite was found to be 3-069, 
and the hardness so great that a slab of fluor-spar became 
dull when rubbed with the powder. 
The solution of phosphate of lime in fused chloride of 
sodium, and its separation on cooling, furnish an excellent 
means of detecting minute quantities of phosphoric acid in 
rocks, &c. For this purpose the powdered substance is heated 
with 50 per cent. of chloride of sodium, which, when the sub- 
stance is tolerably fusible, separates from the silicates as an 
upper layer. When the substance is not fusible, the chloride 
of sodium remains partially mixed with it, in cavities distri- 
buted throughout the mass, and presenting, after the solu- 
tion of the chloride, a remarkable similarity to the vesicular 
cavities of amygdaloid. The small crystals of apatite gene- 
rally project like hairs from the surface of the partially dis- | 
solved mass, and being soluble in very dilute hydrochloric or 
nitrie acid, they may be collected by that means and esti- 
mated. The author has in this way detected phosphoric 
acid in greenstone belonging to the primitive and transition 
formations of Scandinavia; in the greenstone, occurring as 
boulders, in the more recent formations; in that of the trap 
formation of Greenland; in the basalt of Steinheim; in a 
course granular basalt or lava from Iceland; in three varie- 
ties of granite and gneiss from Bornholm, and in two varieties 
of mica schist. From one Bornholm granite, remarkably 
fine and distinct, crystals of apatite were obtained. 
The observation, made some years ago by Fownes, of the — 
presence of phosphoric acid in rocks, thus gains further con- 
firmation, in addition to the testimony of Swanberg and . 
Struve. 
