OF CENTRAL CANADA PART II. 



135 



frequently with rounded edges. Occurs also in 

 lamellar cleavable masses, and occasionally in 

 globular and other shapes with fibrous structure. 

 H = 4.5 - 5.5, normally 5.0. Sp. gr. 2.9 - 3.3, 

 most . ommonly about about 3.18 to 3.2. BB, 

 in most cases quite infusible, but some varieties FIG. 79.* 



vitrify slightly at the point of the assay-fragment after exposure to 

 a long-sustained blast. The powder moistened with sulphuric acid 

 tinges the flame-point distinctly green. Melts and dissolves readily 

 in borax and phosphor- salt, forming a glass which becomes opaque on 

 cooling or when flamed. (See under Blowpipe-reactions in Part I.) 

 Easily soluble in nitric or hydrochloric acid. The diluted solution, 

 saturated with ammonia, yields a copious white precipitate of phos- 

 phate of lime. This precipitate assumes a canary-yellow tint if 

 treated with a solution of nitrate of silver, or if a crystal of that 

 substance be laid in it whilst still moist. The presence of phosphoric 

 acid may also be rendered evident in the diluted nitric acid solution 

 by the formation of a clear-yellow precipitate with molybdate of 

 ammonium.* Apatite consists essentially of phosphate of lime (or 

 calcium, phosphorus and oxygen) combined with in general about 8 

 or 10 per cent, of fluoride of calcium or chloride of calcium, or with 

 a mixture of both, the fluoride usually preponderating. Canadian 

 examples appear to be essentially fluor apatites. The normal com- 

 position of an apatite of this kind is equivalent to : phosphoric acid 

 42.26, lime 55.60, fluorine 3.37 ; or tri basic phosphate of lime 92.26, 

 fluoride of calcium 7.74 ; but samples even when dressed for shipping 

 usually contain a good deal of intermixed calcite and mica scales, and 

 rarely run higher in tribasic phosphate than about 80 per cent. 



Extensive deposits of this mineral^ chiefly in the form of veins, 

 occur in the Laurentian strata of North Burgess and North Elmsley 

 in the County of Lanark. These veins cut the enclosing strata 

 transversely, and vary in width from an inch or two to several feet. 

 The apatite, in crystals, and in cleavable and granular masses, is 

 associated with phlogopite, pyroxene, and other silicates. Where 



* The test-solution is prepared by dissolving some of the crystallilzed molybdate in a very 



small quantity of water, nitric acid being added to the solution until the cloudiness or thick 



> recipitate, which forms at first, becomes redissolved. When this is added to the solution 



of the mineral, the whole must be gently warmed. A yellow coloration, succeeded by a 



yellow precipitate, then quickly ensues. 



