The Sulfides

 These are not common minerals but are prized because of their economic value.  Geologists often make these minerals the target of their exploration.  These minerals are the source of many metals we use today.  These minerals must be refined to separate the metal from the sulfur  The properties they share are metallic lustre, high specific gravity (heavy) and streak.

 Remember to streak all metallic minerals  Have a magnet handy as some sulfides are magnetic.  Remember to wash your hands after handling due to the presence of heavy metals.

PROPERTY ColourCaramel brown to Black Crystal Formrare Cleavage/FractureCommon in 6 directions – as a result the small grains have many smooth cleavage faces which cause the mineral to sparkle! LustreSub-metallic – can be somewhat vitreous HardnessSoft (4) Specific Gravityheavy StreakBrown to black (few minerals streak brown – the other you know is Chromite) OtherCommonly found with Galena (and even Chalcopyrite) in limestone. It is the main ore of zinc (used to galvanize steel)

PROPERTY ColourBrassy yellow Crystal FormCommon (cubes, pyritohedrons, striated crystals) but is usually seen massive Cleavage/Fracturenone LustreMetallic HardnessVery hard (7) – can scratch glass – unusual for a metallic mineral Specific GravityMedium-heavy Streakblack OtherNon-magnetic The most common metallic mineral !– often called “fools gold” due to its brassy colour (this mineral shares almost no other properties with gold) Despite its abundance it has no economic value – most iron ores are iron oxides. It is indicator mineral in many gold mines.

PROPERTY ColourGun-metal grey Crystal FormCommon (cubes, pyritohedrons, striated crystals) but is usually seen massive Cleavage/FracturePerfect in 3 directions 90˚ creating cubic cleavage fragments LustreMetallic – very lustrous cleavage faces HardnessSoft (3) – soft – easily scratched by a nail Specific GravityVery heavy due to the lead – densest mineral in our set. Streakblack OtherCommonly associated with sphalerite. Galena “rusts” to a duller grey Non-magnetic It is the main ore of lead in the world

PROPERTY ColourYellow-gold – the colour is more yellow than pyrite but less golden than gold. Crystal FormAlmost always massive Cleavage/Fracturenone LustreMetallic Hardnesshard (4.5) – cannot scratch glass – can be scratched with a nail Specific GravityMedium-heavy Streakblack OtherNon-magnetic The problem is that it is often associated with pyrrhotite which is magnetic It is a major ore of copper. Used for wiring and pipes.

PROPERTY ColourBrownish metallic Crystal FormUsually massive but can form hexagonal prismatic crystals. Cleavage/Fracturenone LustreMetallic Hardnesshard (5) – cannot scratch glass – can be scratched with a nail Specific GravityMedium-heavy Streakblack OtherMagnetic It is often associated with similarly coloured pyrite and chalcopyrite Odd formula is due to Fe atoms that are often absent in the crystal structure. It has little economic value

PROPERTY ColourBlack sub-metallic to purplish metallic with a common irridescent coloured surface leading to its nickname of “Peacock Ore” Crystal FormUsually massive Cleavage/Fracturenone LustreMetallic-Sub-metallic Hardnesssoft (4) – cannot scratch glass – can be scratched with a nail Specific GravityMedium-heavy Streakblack OtherNon-Magnetic Almost always has a greenish “rust” It is often associated with other copper sulfides such as chalcopyrite It is a secondary ore of copper