396 DETERMINATION OF MINERALS. 



FRANKLINITE, p. 179. H. =5-5-6-5; G. =4-8-5 1; octahedral, 



massive ; iron-black ; streak dark rdh brown ; slightly attracted 

 by magnet ; with soda reaction for manganese. 



COJLUMBXTE. p. 183. G. =5* 4-6 5; trimetric ; iron-black, gyh 

 black, streak dark red to black, often with a bluish steel -tarnish. 



SAMARSKITE, p. 202. H. =5-5-7; GK=5-6-5"8j velvet-black, 

 pitch-black ; streak dark rdh brown ; B.B. glows ; fuses with dif- 

 ficulty. 



b. REACTION FOR IRON ; HYDROUS ; LUSTRE SUBMETATJJC. 



LIMONITE, p. 181. G. =3'6-4 ; massive, often stalactitic and tube- 

 rose with surface sometimes highly lustrous, often subfibrous in 

 structure ; black, bnh black ; streak bnh yellow. 



GOTHITE, p. 182. G. =4-0-44; trimetric; also fibrous and mas- 

 sive ; bkh brown ; streak bnh yellow. 



TURGITE, p. 182. G. = 3 -6-4-6*8 ; fibrous and massive, looking like 

 limonite ; black, rdh black, streak red ; in closed tube decrepitates, 

 which is not the case with gothite and limonite. ' 



C. REACTION FOR CHROMIUM OR TITANIUM. 



CHROMITE, p. 180. H.=5-5; G. =4-3-4-6 ; isometric; submetal- 



lic ; bnh iron-black, streak brown ; B.B. with borax gives a bead 



which on cooling is chrome-green. 

 RUTILE, p. 162. H. =6-6 5; G. =418-4 25 ; black, streak bnh; 



reacts for titanium. Black varieties of brookite (p. 163), submetallic 



in lustre, give same reaction. 



Euxenite, p. 202 ; yttrotantalitc, p. 202 ; asehynite, p. 202; ferguson- 

 ite, p. 202, andperofslcite, p. 1(J3, are submetallic in lustre. 



d. HEATED WITH NITRE IN A MATRASS YIELDS FUMES OF OSMIUM. 



IRIE-OSMINE, p. 127. H.=6-7; G. =19-21 2 ; in small scales 

 from auriferous or platiniferous sands ; tin-white, gyh. 



V. LUSTRE UNMETALLIC. 



1. MINERALS HAYING AX ACID, ALKALINE, 

 ALUM-LIKE, OE STYPTIC TASTE. 



A. CARBONATES : Taste alkaline ; effervescing with HC1. 



NATRON, p. 229. Effloresces on exposure. 

 TRONA, p. 230. Does not effloresce. 



