Geology Reference
In-Depth Information
Leucite
KAlSi
2
O
6
White or grey
None
Vitreous or
resinous
Often euhedral
trapezohedral crystals in
alkaline lavas
5.5 - 6
Hematite
Fe
2
O
3
Redtored-brown,
sometimes black
None
Dull
Usually fine and powdery,
occasionally scaly or
fibrous crystals
5.5 - 6
Magnetite,
(a spinel
mineral)
Fe
3
O
4
Black, brownish-black
Poor
Metallic, dull
Small equidimensional
granular crystals, occasional
cubes or octahedra
5.5
(Other spinels are M
2
+
M
2
3
+
O
4
where M
2
+
is Fe, Mg, Mn, Zn, etc. and M
3
+
is Al, Fe, Cr, etc. e.g. dark brown to black
chromite
,FeCr
2
O
4
, which occurs in some peridotites)
Ilmenite
FeTiO
3
Black, brownish black
or grey
None
Metallic or
dull
Thin plates or scales
usually elongate crystals,
sometimes rod-like
5.6
