396 DETERMINATION OF MINERALS. 
FRANKLINITE, p. 179. H.=5°5-65; G.=—4°8-5:1; octahedral, 
massive ; iron-black ; streak dark rdh brown; slightly attracted 
by magnet ; with soda reaction for manganese. 
COLUMBITE, p. 188. G.=5'465; trimetric; iron-black, gyh 
black, streak dark red to black, often with a bluish steel-tarnish. 
SAMARSKITE, p. 202. H.=55-7; G.=56-5'8; velvet-black, 
pitch-black ; streak dark rdh brown ; B.B. glows ; fuses with dif- 
ficulty. 
b. REACTION FOR IRON ; HYDROUS ; LUSTRE SUBMETALLIC. 
LIMONITE, p. 151. 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.=4:0-4:4; trimetric; also fibrous and mas- 
sive ; bkh brown; streak bnh yellow. 
TURGITE, p. 182. G =3°6-4°68 ; fibrous and massive, looking like 
limonite ; black, rdh black, streak red ; in closed tube decrepitates, 
which is not the case with géthite and limonite. 
C. REACTION FOR CHROMIUM OR TITANIUM. 
CHROMITE, p. 180. H.=—5-5; G.=4°3-46; 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.=6-65; G.=—418-425; black, streak bnh; 
reacts for titanium. Black varieties of brookite (p. 163), submetallic 
in lustre, give same reaction. 
Hurenite, p. 202 ; yttrotantalite, p. 202; eschynite, p. 202; ferguson- 
ite, p. 202, and perofsxite, p. 163, are submetallic in lustre. 
d. HEATED WITH NITRE IN A MATRASS YIELDS FUMES OF OSMIUM. 
IRIDOSMINE, 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 HAVING AN ACID, ALKALINE, 
ALUM-LIKE, OR STYPTIC TASTE. 
A. CARBONATES : Taste alkaline ; cffervescing with HCl. 
NATRON, p. 229. Effloresces on exposure. 
TRONA, p. 230. Does not effloresce. 
