hydroxides Flashcards
how to distinguish oxides from hydroxides
the presence of OH- or H2O molecules
what is the effect of OH- in the bonds
weakens them
brucite formula
Mg (OH)2
brucite form
- hexagonal, tabular
- more commonly foliated massive
brucite cleavage
basal perfect. sectile, flexible folia not elastic
brucite hardness
2.5
brucite specific gravity
2.39
brucite color
- pearly on base, waxy and vitreous elsewhere
- white gray light green
brucite occurrence
- in assoc with serpentine dolomites, magnetite and chromite
- reaction product of Mg silicates, esp serpentine
brucite remarks
foliated nature, light color, pearly on cleavage
how to tell brucite from talc
brucite is harder (2.5) talc is 1
how to distinguish brucite from mica?
brucite is inelastic
manganite formula
MnO (OH)
manganite form
- monoclinic, prismatic parallel to c, vertically striated
- often columnar to coarse, fibrous
- contact and penetration twins common
manganite cleavage
perfect pinacoidal
manganite hardness
4
magnanite specific gravity
4.3
manganite color
- metallic, opaque
- steel gray to iron black. streak is dark brown
manganite occurrence
- in manganese deposits assoc eith other mn oxides and hydroxides
- in low temp veins assoc with barite, siderite and calcite
manganite occurrence
- manganese deposits assoc with other Mn-oxides and hydroxides
- in low-temperature hydrothermal veins associated with barite, siderite, and calcite
what does manganite commonly alter into
pyrolusite
manganite remarks
black color, prismatic, 4 hardness
how to distinguish manganite from pyrolusite
pyrolusite has iron black streak, manganite has dark brown streak
romanechite formula
basta Ba, H2O, mn 4+ 3+ and O10
romanechite form
amorphous, massive botryoidal, stalactitic
romanechite hardness
5-6
romanechite specific gravity
3.7 to 4.7
romanechite color
submetallic opaque. black
brownish black streak
romanechite occurrence
- from secondary alteration of original Mn-carbonates, Mn-silicates, or both
- in assoc with pyrolusite in manganese ore deposits
- in nodular deposits in bogs, and on lake bottoms and on see and ocean floors
former term for the hard botryoidal masses of which are mixtures of manganese oxides of which romanechite is a major constituent
psilomelane
how to distinguish romanechite from other manganese oxides?
its hardness and botryoidal form
how to distinguish romanechite from limonite
romanechite has a brownish black streak
geothite formula
FeO (OH)
geothite form
- rarely orthorhombic prismatic, vertically striated
- massive, reniform, stalactitic in radiating fibrous aggregation
- foliated
loose and porous geothite
bog ore
geothite cleavage
pinacoidal perfect
geothite hardness
5 to 5.5
geothite specific gravity
4.37, if impure as low as 3.3
geothite color
- adamantine to dull, silky, scaly fibrous
- yellowish brown to dark brown
- yellowish brown streak. subtranslucent
geothite occurrence
- common resulting from oxidation and weathering of iron bearing minerals
- widespread in bogs and around springs
where is geothite in metalliferous vein deposits?
the iron hat, the gossan
how to distinguish geothite from colloform hematite and romanechite
hematite is black to brownish red
geothite is yellowish brown to black and
romanechite is just black
limonite formula
FeO (OH) nH2O
field term used for very fine grained to amorphous mictures of brown ferric hydroxides with unknown real identities
limonite
commonly, what is the biggest composition of limonite
geothite
T or F bauxite is a mineral/mineral species
F, it is a rock term
bauxite consists of very fine grained intergrowth of three aluminum oxides, what are they
diaspore, gibbsite and boehmite
bauxite is what type of ore
major aluminum ore
bauxite form
- micture, pisolitic round concretionary grains
- also massive, earthy claylike
bauxite hardness
1-3
bauxite specific gravity
2 to 2.55
bauxite color
dull earthy
- white gray red yellow
what causes yellow color of bauxite
limonite staining
bauxite occurrence
- eupergene, in subtropical or tropical conditions, prolonged weathering and leaching of silica from aluminum bearing rocks
soil consisting mainly of hydrous aluminum and ferric oxides
laterite
bauxite remarks
light, yellowish brown color, pisolitic, earthy tecture and low degree of hardness