128 Mr HAIDINGER'S Mineralogical Account of 



Simple forms. | P 4 (a) 139 56', 57 57'; P_l = 

 114 51', 99 11'; P(P). 



Char, of comb, pyramidal. 



Combinations. 1. *- P 4. P. Fig. 15. 

 2. | P_4. P 1. P. 



Cleavage, P GO rather perfect ; P 1 and P less distinct, and 

 interrupted. Fracture uneven. Surface, * P 4, very smooth and 

 shining, P horizontally streaked, and often dull. 



Lustre, imperfect metallic. Colour, brownish-black. Streak, 

 dark-reddish, or chesnut-brown. Opaque. 



Hardness 5.0, 5.5, a little higher than apatite. Sp. gr. =. 

 4.722, of a crystallized variety. 



Compound Varieties. Twin crystals : axis of revolution per- 

 pendicular, face of composition parallel to a face of P 1, Fig. 16. 

 The composition is often repeated parallel to all the faces of the 

 pyramid, Fig. 17. Generally small particles only of the surround- 

 ing individuals are joined to the central one. Massive : compo- 

 sition granular, firmly connected. 



Observations. 



Professor HAUSMANN, in compliment to whom Dr TURNER and 

 myself propose to call the present species " Hausmannite" ranks 

 so high among the professors of his science, that it must appear 

 much more extraordinary, no species should as yet commemorate 

 his name, than that we should pay this tribute of friendship and 

 respect to that distinguished individual. He has been accustomed 

 in his lectures, subsequent to the publication of his work, to point 

 out the present species as a peculiarly remarkable substance, of a 

 nature not yet exactly ascertained. 



It would be superfluous to enlarge here on the propriety of 

 considering it as a species of its own, since, besides Mr MOHS, it 



