58 CALIFORNIA ACADEMY OF SCIENCES. 



The clearest crystals obtainable contained small quan- 

 tities of soda, varying from to 26-100 per cent, to 54-100 

 per cent., reckoned as caustic soda, but undoubtedly pres- 

 ent as borate of soda. This is probably a mechanical 

 admixture, and does not enter into the mineral as an 

 essential element. It points, however, very strongly to 

 the origin of the mineral from ulexite. By inspection of 

 the formula, we observe that if the soda be abstracted 

 from ulexite along with its equivalent of boric anhy- 

 dride (2B_. O3), there remains a compound identical with 

 Colemanite or pandermite in its ratio of boric acid to the 

 lime. In fact, both Colemanite and pandermite have been 

 produced artificially by deposition from aqueous solutions 

 of ulexite, the temperature alone determining the degree of 

 hydration. Under varying conditions of temperature, con- 

 centration and pressure different, and yet closely allied, hy- 

 drous borates of lime would be deposited, and this might 

 tike place in quick succession, or even simultaneously in dif- 

 ferent portions of the same bed or ledge. These borates are 

 thus very closely allied in their origin, and are liable to 

 glide one into another by insensible gradations. Hand speci- 

 mens are found having all the appearance of ulexite atone ex- 

 tremity and Colemanite at the other. This may account for 

 some of the apparent discrepancies in the analysis by re- 

 putable chemists. Pisani's analysis of pandermite (quoted 

 by the State mineralogist), is that of Priceite pure and 

 simple. 



Specimens of borate of lime having all the appearance of 

 the massive variety of Colemanite, have given results on 

 analysis closely agreeing with the formula of Priceite. 



As far as we are informed, Colemanite is the first definite- 

 ly crystallized borate of lime hitherto found. 



With reference to its susceptibility of reduction to boric 

 acid or borax, practical tests have shown it to be quite 

 refractory. 



