314 



Mr. Shepard's reply to Prof. Del Rio. 



Characteristic of Breithaupt. 



To determine the order. 



Order I. of Class III. Ores 



Metallic lustre : the mineral is 



excluded. 

 Common lustre : H. 1-0 ... 9*0 

 G. 2-1 ... 8*1, which brings it 

 here unless excluded by what 

 follows. 



H. 10 . . . 2-5. 

 H. 2-50 . . . 4-25 

 H. 4-50... 6-0. 

 H.6-0 ...80. 

 H.8-0 ... 9-0: 

 more, which 

 mineral to fall within this 

 order. 



Excluded. 



Excluded. 



Excluded. 



Excluded. 

 G. 4-1 and 

 proves our 



My Ciiaracteristic. 



To determine the order. 



If a crystal, the order is the 7th, 

 of Class I., the Right square 

 prism. 



If a cleavable variety, the order 

 is the 5th of Class II., the Right 

 square prism. 



If an uncleavable variety, it falls 

 in Class III., between Species 

 221 and 285, which is the order 

 of Rutile for this class, there be- 

 ing 64 species whose hardness is 

 within unity above or below it, in 

 the scale of hardness. 



To determine the genus* 

 Genus 1st. of order I. Class 



III. Gadolinite. 

 Deuterostatic. It is excluded. 



Genus 2nd. Tephroite. 

 Protostatic. Tetragonal, brachyax. 



Cleavage lateral. 

 H. 7-0, but the hardness of the 

 mineral sought is S'O . . . 9*0. 

 Genus 3rd. Hard- Ore. 

 Protostatic. Tetragonal, holoe- 

 dric, brachyax. Cleavage lat- 

 eral, distinct to perfect. 

 H. 7-50 . . . 9-0. 

 G. 4-20-. . .7-1. It belongs here. 



To determine the species. 

 Species 1st. of Genus Hard- 

 Ore. Rutile Hard-Ore. 



To determine the species. 

 If crystallized, compare in Sp. 

 Gr. the species Nos. 8, 9, and 10. 



* As Prof. DezlRio has carried the translation no farther than through the or- 

 ders, I avail myself, in pursuing the analysis, of the original work. 



