58 Dr. Clarke on Arragonite. [July, 



decisive as to its being arragonite, its specific gravity might 

 excite a reasonable hesitation ; because, although it agree with 

 the specific gravity given, of arragonite by Brochant,* from 

 Gellert ; namely, 2*7 ; this does not correspond with Haiiy's 

 statement,-)- which makes the specific gravity of arragonite as 

 high as 2 - 9. But the discrepancy, as will further appear in the 

 sequel, admits of obvious explanation ; the one being the spe- 

 cific gravity of stalactite arragonite ; the other, namely, that of 

 Haiiy, the specific gravity of crystallized arragonite. J 



Previous to any additional remarks upon the nature of a sub- 

 stance so paradoxical as arragonite is allowed to be by all mine- 

 ralogists, it will be necessary to define specifically the identical 

 mineral to which this name is here applied. By arragonite is 

 intended a variety of carbonate of iime distinguished from com- 

 mon lime spar in the following characters : 



1. Superior hardness, being hard enough, in some instances, 

 to scratch glass ; but in all to make a deep incision into Iceland 

 spar, and even to cut fluor spar ; therefore called chaux car- 

 bonatee dure. 



2. Superior specific gravity when crystallized. 



3. A scopiform structure, often exhibiting diverging fibres, 

 radiating from a common centre. 



4. Small fragments rendered opaque and friable in the flame 

 of a common candle exhibiting also a mouldering dispersion into 

 particles by means of the common blowpipe. This mouldering 

 dispersion into particles by means of heat is more particularly 

 characteristic of the crystallized varieties of arragonite. It 

 nevertheless belongs to the radiated arragonite in stalactites at 

 the cavern of Antiparos. 



5. Phosphorescence, with a green light. This property, 

 however, cannot be considered as discriminative ; because it 

 is also possessed by some of the sub-varieties of common car- 

 bonate of lime. 



6. Irreducible by fracture into the primary form of carbonate 

 of lime. Either exhibiting rhombi more obtuse than those of 

 common carbonate of lime ; or, in some instances, disclosing no 

 rhomboidal fracture. 



As long as arragonite shall continue to offer the only anomaly 

 in Haiiy's theory of crystallization, and the cause of that anomaly 

 shall continue to baffle the researches of chemists, so long will 

 it be regarded as the most remarkable of mineral bodies. " The 

 analysis of no mineral,'' says Prof. Cleaveland,§ *' has ever so 



* Traitt- de Mineralogie, torn. i. p. 577. Paris, 1808. 



■f Traite de Mineralogie, torn. iv. (Ito Edit.) p. 240. Paris, 1801. 



X Le caractere de la pesanteur est necessairement soumis a quelques variations, soit 

 a. raison des different* melanges, qui peuvent se rencontrer dans les substances qu'on 

 examine sous ce rapport, soit a raison de la reunion plus ou moins exacte, entre elles, de 

 toutes les molecules integrantcs qui sont entrees dans leur formation. — (Bournon, Traite, 

 &c. vol. i. p. 14. Lond. I80<J.) 



§ Treatise on Slineralogy and Geology, by Prof. Cleaveland, p. 180. Boston, 1816. 



