Introduction to the Study of Mineralogy, 467 



fc In short, the modifications relative to colours, trans- 

 parency, or opacity, will be indicated in their turns, and 

 will form as it were the last shades of the picture. " 



Thus a specific gravity of about triple that of water, a 

 hardness equal at most to that of such bodies as slightly 

 scratch glass, natural joints parallel to the faces and to the 

 bases of a regular hexahedral prism, the property of dissolv- 

 ing without effervescence in the nitric acid, will easily as- 

 certain that a crystal provided with these properties belongs 

 to the species of phosphated lime; and if it is a regular 

 hexahedral prism terminated by hexahedral pyramids, the 

 faces of which are inclined to each other by about 129°*, 

 this particular character will point out the variety which I 

 denominate pyramidatcd phosphated lime ; and the conse- 

 quence already deduced from the specific character with re- 

 spect to the nature of the crystal observed, will even then 

 become an evidence, so much the more striking, that this 

 measure of 129° would alone be sufficient for indicating a 

 primitive form of phosphated lime; the analogous inclina- 

 tion being different in the forms of the same genus which 

 belong to other species f. If the same crystal has trans- 

 parency, if it is of an orange colour, as we find it in Spain, 

 the indication of these accidental circumstances will com- 

 plete its denomination, and the observer can place it in his 

 collection, with this inscription, phosphated lime, pyramidal 

 orange transparent. 



But this will not be a crystal ; it will be an irregular mass, 

 in which the geometrical type of the species will have dis- 

 appeared, and the aspect of it will excite a doubt in the ob- 

 server, if what he sees be not a coarse carbonated lime, 

 similar to what we call building-stone (pierre a hath). His 

 doubts will be dispelled, when, having put a small fragment 

 of this mass into the nitric acid, 1 e will obtain a slow and 

 tranquil solution, or at the most accompanied oy a slight 

 effervescence ; when, having thrown some of it in pow e'er 

 upon lighted charcoal, he will see a fine phosphoric li^ht pro- 



* More strictly speaking, 129° 13'. 



f Quartz, carbonated barytes, pbgsphated lead. 



G g 2 . duced 



