614 MANUAL OF NATURAL HISTORY. 



iron in " Ferro-tantalite," H. 5 6 ; sp. gr. 

 = 7'5 ; black, brittle. Symb. Ta. 



3. FAMILY. Niobiides. Minerals containing com- 



pounds of Niobium. Occur as Niobic acid 

 in "Polycrase," also in "Niobite." Symb. 

 Nb. 



4. FAMILY. Pelopiides. Minerals containing com- 



pounds of Pelopium. Occur as Pelopic acid 

 in " Polycrase," also in " Columbite." Symb. 



PP. 



5. FAMILY. Ilmeniides. Minerals containing com- 



pounds of Ilmenium. Supposed to exist in 

 "Samarskite." Symb. II. 



6. FAMILY. Kassiterides. Minerals containing Tin, 



either native, or in combination. Occur 1, 

 pure or " Native Tin/' in grains with Siberian 

 gold, sp. gr. 7'2 ; 2, as Binoxide or " Cas- 

 siterite" or "Tin Ore," H. = 6'5, sp. gr. = 

 6 '8, crystallised, massive, or in grains, 

 brown or black ; 3, as Sulphuret or " Tin- 

 pyrites," in cubes, H. 4 ; sp. gr. 4 '4, steel- 

 gray. Oxide of tin before the blowpipe, 

 with soda, yields metallic tin, and with borax 

 an opal white enamel. Symb. Sn. 



7. FAMILY. Titaniides. Minerals containing Tita- 



nium, either native or in combination. Oc- 

 cur 1, pure as " Native Titanium," in copper- 

 red cubes, in Cornwall, H. = 7, sp. gr. = 5 '3 ; 

 2, as Titanic acid or " Rutile," prismatic, 

 H. = 6, sp. gr. = 4*2, reddish brown, also 

 combined with oxide of iron or some other 



