106 PHYSIOGRAPHY. 



Calcareous Spar. 



Massive: 1. Composition columnar, the individuals be- 

 ing straight, parallel, or diverging, very often of remarka- 

 ble delicacy. In a second composition, globular masses are 

 produced, consisting of curved lamellar particles, the faces 

 of composition between the latter often being smooth. 

 These globules are again joined in a third composition, pro- 

 ducing granular masses, between which the faces of compo- 

 sition are uneven and rough. 2. Composition granular, 

 the individuals being of various sizes, and even impalpable ; 

 faces of composition irregularly streaked, uneven and 

 rough. The individuals cohere more or less firmly. If 

 the composition be impalpable, fracture becomes splintery, 

 uneven, flat, conchoidal, or even ; on a large scale it is 

 sometimes slaty. The fracture is earthy in those varieties 

 in which the individuals cohere but slightly. 3. Composi- 

 tion lamellar ; the indviduals more or less thin, and often 

 bent ; face of composition sometimes rough, and possessing 

 a pearly lustre. Globules formed in cavities ; plates, of 

 various kinds of composition. 



1. The species of Calcareous Spar, as at present regarded by the ma- 

 jority of mineralogists, probably embraces several distinct species, sepa- 

 rated from one another by constant differences of form, hardness and 

 specific gravity. An attempt has been made within a few years by 

 BREITHAUPT, to determine, by some of the nicest mineralogical re- 

 searches of modern times, a number of such species. But as the differ- 

 ences upon which he founds his conclusions are so slight, in comparison 

 with specific differences in general in the mineraal kingdom, it seems 

 most judicious for the present to introduce his results in the form of an 

 appendix to this species, where they will be found given in sufficient de- 

 tail to enable the mineralogical student to appreciate their value. 



The division of Calcareous Spar into several sub-species and varieties, 

 in the older treatises on the science, depends chiefly upon the mode of 

 composition, and upon admixtures and impurities, with which the indi- 

 viduals have been affected in their formation. Of these Limestone rep- 



