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Ore Minerals Cheat Sheet (DRAFT) by

A guide to ore minerals

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Ore Mineral

Arseno­pyrite
H: 5.5-6
Silver­-white
1 poor cleavage
Associated with silver and copper ores, galena, sphale­rite, pyrite, chalco­pyrite, and gold
The principal source of Arsenic
Azurite
H: 3.5-4
Intense azure-blue
2 cleavage at almost 90
Associated with Malachite
A minor ore of Copper
Barite
H: 3-3.5
Colour­less, white, grey
2 cleavage planes
Associated with ores of silver, lead, copper, cobalt, manganese, and antimony
Chief source of Ba in chemicals, 80% used for heavy mud in mining
Bauxite
H: 1-3
White, grey, yellow, red (trans­lucent)
No cleavage, fractures around pisolitic balls
Alloyed with copper, manganese, zinc, nickel, silica, silver, and tin
The ore of Aluminium, 85% consumed as aluminium ore
Bornite
H: 3
Browni­sh-­brown on fresh fracture
Fractures
Associated with chalco­cite, chalco­pyrite, covellite, pyrrho­tite, and pyrite
A copper ore
Cassit­erite
H: 6-7
Brown or black
1 imperfect cleavage
Associated with Stannite
A principal ore of Tin
Chromite
H: 5.5
Iron-black to browni­sh-­black
No cleavage
Associated with perido­tites and ultrabasic rocks
The only ore of Chromium
Chalco­pyrite
H: 3.5-4
Brass-­yellow
No cleavage
Associated with galena, sphale­rite, dolomite, pyrrhotite and pentla­ndite
An important ore of copper
Fluorite
H: 4
Varies; commonly light-­green, yellow, blue-g­reen, or purple
1 perfect cleavage
Associated with calcite, dolomite, gypsum, celestite, barite, quartz, galena, sphale­rite, cassit­erite, topaz, tourma­line, and apatite
Used in the chemical industry
Galena
H: 2.5
Lead-grey
1 perfect cleavage
Associated with sphale­rite, pyrite, marcasite, chalco­pyrite, cerussite, anglesite, dolomite, calcite, quartz, barite, and fluorite
The only source of lead and an important ore of silver
Goethite
H: 5-5.5
Yellow­ish­-brown to dark brown
1 perfect cleavage
Associated with weathered serpentine and iron-b­earing minerals
An ore of Iron
Gypsum
H: 2
Colour­less, white, grey
3 cleavage planes
Associated with halite, anhydrite, dolomite, calcite, sulphur, pyrite and quartz
Industrial use
Hematite
H: 5.5-6.5
Reddis­h-brown to black
2 cleavage planes
Associated with maghemite
Most important ore of Iron for steel manufa­cture
Ilmenite
H: 5.5-6
Iron-black
No cleavage
Associated with Geikelite, pyroph­anite
A major source of Titanium
Magnetite
H: 6
Iron-black
Octahedral parting sometimes visible
Associated with ulvosp­inel, magnes­iof­errite, jacobsite, magher­mite, maritite
An important Iron ore
Malachite
H:3.5 - 4
Bright green
Perfect cleavage, but rarely seen
Associated with azurite, cuprite, native copper, iron oxides
A minor ore of Copper
Molybd­enite
H: 1-1.5
Lead-grey
1 perfect cleavage
Associated with cassit­erite, scheelite, wolfra­mite, fluorite, and chalco­pyrite
The principal ore of molybdenum
Pentla­ndite
H: 3.5-4
Yellow­ish­-bronze
1 cleavage
Associated with pyrrhotite
The principal ore of nickel
Pyrite
H: 6-6.5
Pale brass-­yellow
Conchoidal fracture
Associated with chalco­pyrite, sphale­rite, and galena
Mined for copper or gold associated with it
Pyrolusite
H: 1-2
Iron-black
1 perfect
Associated with veins with quartz and various metallic minerals
Most important Manganese ore
Pyrrhotite
H: 4
Browni­sh-­bronze
No cleavage
Associated with pentla­ndite, chalco­pyrite or other sulphides
Mined for its associated nickel, copper, and platnium
Rhodonite
H:5.5-6
Rose-red, pink, brown
2 perfect cleavages
Associated with manganese and mangan­ese­-rich iron deposits
Ornamental stone
Scheelite
H: 4.5-5
White, yellow, green, brown
1 distinct cleavage
Associated with cassit­erite, topaz, fluorite, apatite, molybd­enite, and wolframite
An ore of Tungsten
Sphalerite
3.5-4
Colourless when pure, green when almost pure
1 perfect cleavage (can be hard to see)
Associated with pyrrhotite
The more important ore of zinc
Stibnite
H:2
Lead-grey to black
1 perfect
Associated with antimony minerals, galena, cinnabar, sphale­rite, barite, realgar, orpiment, and gold
The chief ore of antimony
Wolframite
H: 4-4.5
Dark
1 perfect cleavage
Associated with cassit­erite, scheelite, bismuth, quartz, pyrite, galena, sphale­rite, and arseno­pyrite
Chief ore of Tungsten
 

Ore textures

Massive sulphide
Greater than 50% of the rock is of sulphide minerals. Textures include massive, banded, brecci­ated. Grain size varies from fine grained to coarse grained. Sulphide mineralogy is dependent upon the individual minera­lising system
Cumulate textures
Primary magmatic processes when heavy minerals, crysta­llised in a magma, are able to sink to the bottom of the magma chamber and cumulate. This may lead to economic concen­tration of minerals
Semi-m­assive sulphides
An r ore that contains signif­icant amounts of sulphide minerals, but not exceeding 50%
Stringer ore
Developed where fluid pathways exist in an ore system. As the fluids migrate, they may deposit ore minerals and cause signif­icant hydrot­hermal alteration of the host rock. Stringer zones are essent­ially the plumbing system and may contain ore grade
Breccia
Hydrot­hermal breccias are common hosts to ore. These ores form during or after brecci­ation of the host rock, due to tectonic forces or hydraulic pressure
Vughs and open space fillings
These textures are indicative of low temper­atures where there is low lithos­tatic pressure and the ore system is developing at or near the Earth’s surface. For this reason, open space voids may be developed
Veins
Vein hosted ore is very common in hydrot­hermal systems as the fluids carrying metals also carry gangue mineralogy compon­ents. Commonly, the gangue minerals precip­itate with the ore minerals to form veins in the fluid pathways
Replac­ement ore
Replac­ement ores may be massive, semi-m­assive or dissem­inated, depending on the ore system. They generally show prefer­ential replac­ement of one or more original components of the host rock. In some cases, ore minerals prefer­ent­ially replace host rock components
Recrys­tal­lis­ation
Recrys­tal­lis­ation is relatively common in many ore systems where early formed ore minerals may be either remobi­lised or recrys­tal­lised due to later thermal or hydrot­hermal events. Recrys­tal­lis­ation textures impart metamo­rphic textures to the rock
Dissem­inated ore
Dissem­inated ore is one of the most common ore types. It is finely dissem­inated, or irregu­larly distri­buted ore mineral within a host rock. Many dissem­inated ore zones form the low grade periphery of a deposit. In some ore systems however, they may be the high grade zones
Supergene ore
Supergene processes occur in an oxidising enviro­nment, at or above the water table. These rocks are either the weathered product of hypogene ore, or are enriched by ground­water mobili­sation then precip­itation of metals to forms supergene ores. They are ores of copper, iron and lead
Ductile ore
At high temper­atures during ore formation, ductile textures result. Rather than brittle fracturing and brecci­ation, replac­ement and mylonitic textures are developed
Greisen
Highly altered granitic rock or pegmatite at the top of an intrusive body
Pendant
Remnant of overlying country rock protruding onto a plutonic body.