Tuesday, August 31, 2010

⤱ Hellyerite ⤱

Hellyerite is a very rare and unstable nickel carbonate mineral with a formula of NiCO3.6H2O.

This specimen is from the Type Locality, the Lord Brassey Mine, Heazlewood district, Tasmania.

⤱ Hannayite ⤱

Hannayite is a very rare phosphate mineral that forms in cave guano. Its formula is (NH4)2Mg3H4(PO4)4.8H2O.

This specimen is from the Type Locality, Skipton Cave, Victoria.

⤱ Epidote ⤱

Epidote is a pistachio green silicate mineral that usually forms as transparent prismatic crystals. Its formula is Ca2(Fe,Al)3(SiO4)3(OH).

This specimen is from the Mitchell Plateau in the Kimberley region of Western Australia.

⤱ Beryl ⤱

Beryl is a beryllium silicate, formula Be3Al2Si6O18, and provides us with a number of gem varieties such as emerald (green), aquamarine (blue) and morganite (pink). It often occurs as prismatic crystals embedded in the surrounding matrix and can be difficult to extract without damage.

This is a specimen of green emerald beryl from Bullabulling in Western Australia.

⤱ Azurite ⤱

Azurite is a deep blue common secondary copper carbonate mineral found in the oxidised zone of copper ore bodies. Its formula is Cu3(CO3)2(OH)2.

This specimen is from Girilambone, New South Wales.

⤱ Libethenite ⤱

Libethenite is a green copper phosphate mineral with a formula of Cu2PO4OH.

This specimen is from Girilambone, New South Wales.

⤱ Pseudomalachite ⤱

Psuedomalachite is a blue-green copper phosphate often confused with malachite. Crystals are rare. Its formula is Cu5(PO4)2(OH)4.

This specimen is from Girilambone, New South Wales.

⤱ Libethenite ⤱

Libethenite is a green copper phosphate mineral with a formula of Cu2PO4OH.

This specimen is from Girilambone, New South Wales.

Thursday, August 26, 2010

⤱ Libethenite ⤱

Libethenite is a green copper phosphate mineral with a formula of Cu2PO4OH.

This specimen shows the typical triangular crystal cross-section and is from Girilambone, New South Wales.

⤱ Sphalerite ⤱

Sphalerite is a zinc sulphide that can have varying amounts of iron, and that forms as crystals that may be almost colourless through orange, red and brown to almost black, and occasionally green. Its formula is ZnS.

This specimen is from the Que River Mine, Tasmania and also contains small silver galena.

⤱ Pyrite ⤱

Pyrite is a common mineral and sometimes mistaken for gold (known as "Fool's Gold" and "Iron Pyrites"). It is brassy yellow and metallic and generally forms as cubes. Its formula is FeS2.

The surface of the cubes on this specimen have tarnished. It comes from Corop, Victoria.

⤱ Barite ⤱

Barite, also spelled baryte, is a barium sulphate mineral with a formula BaSO4

This is a specimen from Corop, Victoria, and is rare at the locality.

⤱ Dravite ⤱

Dravite is one of the tourmaline group of minerals, usually brown in colour, and with a formula of NaMg3Al6(BO3)3Si6O18(OH)4.

This specimen is from Yinnitharra in Western Australia and clearly shows an inclusion of another mineral, possibly monazite?

⤱ Ferrimolybdite ⤱

Ferrimolybdite is a fibrous yellow alteration product of molybdenite. Its formula is Fe2(MoO4)3.nH20.

This specimen is from Mt Moliagul, Victoria.

⤱ Calcite ⤱

Calcite is a calcium carbonate mineral and has more crystal forms than any other mineral species. Its formula is CaCO3.

This is a specimen of 'agate-patterned calcite'  locally called 'eye agates' that forms as infillings of vescicles in basalt, and is from Kitty Miller Bay, Phillip Island, Victoria.

⤱ Opal ⤱

Opal is an amorphous form of silica with a formula of SiO2.nH2O. Opal without 'fire' is usually referred to as potch. Colourless opal that forms as spheres is known as hyalite, and this form is often fluorescent under UV light. The form that has 'fire' or a play of colour is known as precious opal.

This specimen is boulder opal (Yowah Nut) from Yowah, Queensland.

⤱ Copper ⤱

Copper is one of the native elements, formula Cu. It has been known, mined and used for thousands of years. It often forms as crystals or groups of crystals, sometimes forming branching or dendritic groups.

This unusual specimen is from Broken Hill, New South Wales.

⤱ Smithsonite ⤱

Smithsonite is a zinc carbonate mineral with a formula of ZnCO3. It is common in the oxidised zone of zinc ore deposits. Smithsonite can occur as individual rhombohedral crystals, or more commonly, aggregates that form spherical groups.

This specimen is from the Kintore Open Cut, Broken Hill, New South Wales.

⤱ Cerussite ⤱

Cerussite is a lead carbonate mineral with a formula of PbCO3. It is common in the oxidised zone of lead ore deposits. Most crystals are colourless, white or cream.

This specimen is from the Block 14 Open Cut, Broken Hill, New South Wales.

⤱ Smithsonite ⤱

Smithsonite is a zinc carbonate mineral with a formula of ZnCO3. It is common in the oxidised zone of zinc ore deposits. Smithsonite can occur as individual rhombohedral crystals, or more commonly, aggregates that form spherical groups.

This specimen is from the Kintore Open Cut, Broken Hill, New South Wales.

Wednesday, August 25, 2010

⤱ Clinochlore ⤱

Clinochlore is one of the chlorite group of minerals with a formula of (MgFe)5Al(Si3Al)O10(OH)8 and is usually green.

This specimen is unusual in that it is colourless. It comes from Mt Lightning, near Coolac, New South Wales.

⤱ Cerussite ⤱

Cerussite is a lead carbonate mineral with a formula of PbCO3. It is common in the oxidised zone of lead ore deposits. Most crystals are colourless, white or cream. So-called 'chrome' cerussite is a yellow form.

This specimen is from the Magnet Mine, near Waratah, Tasmania, the Type Locality for 'chrome' cerussite.

⤱ Spessartine ⤱

Spessartine is one of the garnet group minerals and has a formula of Mn3Al2(SiO4)3. It is usually red or orange in colour, and occurs as transparent to translucent distinct crystals.

This specimen has formed as a sharp crystal and is from the Kintore Open Cut, Broken Hill, New South Wales. Spessartine is common, even characteristic, at this locality.

⤱ Thomsonite-Ca ⤱

Thomsonite is one of the zeolite group of minerals and occurs as colourless thin prismatic crystals with a rectangular cross-section, or else as white fibrous masses or hemispheres. Its formula is NaCa2Al5Si5O20.6H2O.

This specimen is from the Waitakere Volcanics, West Auckland, North Island, New Zealand.

⤱ Siderite ⤱

Siderite is a common iron carbonate that is usually brown in colour and often forms rhombohedral crystals. Its formula is FeCO3.

This specimen is from Bicker's Quarry, a basalt quarry near Tokatoka, Northland, North Island, New Zealand.

Tuesday, August 24, 2010

⤱ Analcime ⤱

Analcime (sometimes known as 'analcite') is a common member of the zeolite group of minerals with a formula of Na2Al2Si4O12.2H2O and occurs as colourless trapezohedral crystals in cavities in volcanic basalt rocks. Often, these crystals 'craze' and turn white after being exposed. Crystals may also appear to be the same colour as the underlying matrix, they are so transparent.

This specimen is from Bicker's Quarry, a basalt quarry near Tokatoka, Northland, North Island, New Zealand.

⤱ Gypsum ⤱

Gypsum is a very soft calcium sulphate mineral that can be scratched with a fingernail, and is also water-soluble. It may occur as colourless transparent crystals with a high lustre, "rams's horn" curved crystals, and fishtail twins. It has a formula of Ca(SO4).2H2O.

This specimen is from Bicker's Quarry, a basalt quarry near Tokatoka, Northland, North Island, New Zealand.

⤱ Axinite-(Fe) ⤱

Axinite-(Fe) or ferroaxinite is the iron-rich member of the axinite group of borosilicates, and forms brownish crystals. Its formula is Ca2FeAl2BO3Si4O12OH.

This specimen is a single crystal from Colebrook Hill, near Rosebery, Tasmania.

⤱ Heulandite ⤱

Heulandite is the name given to a series of zeolite minerals and characteristically have a coffin-shaped habit. They are usually colourless, but can be orange to red.

This specimen is from the Garawilla Volcanics in New South Wales.

⤱ Dolomite, Arsenopyrite ⤱

Dolomite is a magnesium-bearing carbonate mineral, formula CaMg(CO3)2, and often occurs as saddle-shaped crystals. Arsenopyrite is an iron arsenic sulphide mineral that occurs as silver crystals. It's formula is FeAsS.

This specimen has spherical aggregates of dolomite crystals with well-formed arsenopyrite crystals from the Renison Mine, Tasmania.

Monday, August 23, 2010

⤱ Natrolite ⤱

Natrolite is a colourless prismatic zeolite mineral that has a characteristic square cross-section. It's formula is Na2Al2Si3O10.2H2O.

This specimen from Marrawah, Tasmania, has a small calcite crystal attached to one of the prisms.

⤱ Spessartine ⤱

Spessartine is one of the garnet group minerals and has a formula of Mn3Al2(SiO4)3. It is usually red or orange in colour, and occurs as transparent to translucent distinct crystals.

This specimen has formed as a sharp deep red crystal and is from the Kintore Open Cut, Broken Hill, New South Wales. Spessartine is common, even characteristic, at this locality.

⤱ Mesolite ⤱

Mesolite is a white fibrous zeolite mineral with a formula of Na2Ca2Si9Al6O30.8H20.

This specimen has mesolite with minor lévyne infilling a cavity in basalt from Sunderland Bluff, south coast of Phillip Island, Victoria.

⤱ Pyromorphite ⤱

Pyromorphite is a common secondary lead phosphate mineral that occurs in lead ore deposits. It's formula is Pb5(PO4)3Cl and it occurs generally as prismatic, sometimes tabular, green or brown hexagonal crystals.

This specimen is an unusual branching group from Brown's Prospect, Rum Jungle, Northern Territory.

⤱ Pyromorphite ⤱

Pyromorphite is a common secondary lead phosphate mineral that occurs in lead ore deposits. It's formula is Pb5(PO4)3Cl and it occurs generally as prismatic, sometimes tabular, green or brown hexagonal crystals.

This specimen is from the Block 14 Open Cut, Broken Hill, New South Wales.

⤱ Stolzite ⤱

Stolzite is a lead tungstate mineral, formula Pb(WO4), and occurs as tabular or bipyramidal crystals that are commonly yellow, orange or red.

This specimen is from Broken Hill, New South Wales, a locality well-known for excellent specimens in the earlier days of mining.

⤱ Löllingite ⤱

Löllingite is an iron arsenic sulphide mineral that occurs as silver crystals or masses and can be easily confused with arsenopyrite. It's formula is FeAs2.

This specimen is embedded in the typical garnet sandstone from Broken Hill, New South Wales.

⤱ Sulphur ⤱

Sulphur is a native element, formula S, that normally occurs as transparent or translucent yellow crystals. It occurs in areas of active volcanism, particularly around fumeroles or volcanic vents, and in orebodies as a result of the breakdown of sulphide minerals.

This specimen has a tiny but very bright crystal of sulphur sitting alonside brown pyromorphite in cavities in galena. It is from the Kintore Open Cut, Broken Hill, New South Wales.

⤱ Spessartine ⤱

Spessartine is one of the garnet group minerals and has a formula of Mn3Al2(SiO4)3. It is usually red or orange in colour, and occurs as transparent to translucent distinct crystals.

This specimen has formed as a rounded crystal and is from the Kintore Open Cut, Broken Hill, New South Wales. Spessartine is common, even characteristic, at this locality.

Saturday, August 21, 2010

⤱ Dolomite ⤱

Dolomite is a magnesium-bearing carbonate mineral, formula CaMg(CO3)2, and often occurs as saddle-shaped crystals.

This specimen comes from the Olympic Dam deposit, Roxby Downs, South Australia, and there are small hemispheres of hematite present.

⤱ Fluorite ⤱

Fluorite is a halide, formula CaF2, that occurs as cubic crystals, or more rarely as octahedral crystals.

This specimen is from the Pelion Mine, Oakleigh Creek, Tasmania, an area now included as part of the South West Wilderness area. The cube faces have been etched by geological processes.

⤱ Albite ⤱

Albite is one of the feldspars with a formula of NaAlSi3O8. The "sunstone" variety, such as the one shown here from the Harts Range, Northern Territory, gets its name from the platelets inside the crystal.

⤱ Gartrellite ⤱

Gartrellite is a lead copper iron arsenate mineral with a long formula - Pb(CuFeZn)2[AsO4,SO4]2.2(H2O,OH). It usually occurs as earthy green masses such as this one from Ashburton Downs in Western Australia.

⤱ Bismuth ⤱

The element bismuth sometimes occurs as a whitish silver native metal, often tarnished (formula Bi), or may be a constituent of another mineral.

In this specimen from Wolfram Camp in Queensland, native bismuth occurs with bismuthinite wires.

⤱ Alstonite ⤱

Alstonite, Rosebery, Tasmania.

⤱ Albite ⤱

Albite with smoky quartz and feldspar, Tulendeena, Tasmania.

⤱ Agardite-(Y) ⤱

Agardite-(Y) from Dome Rock, South Australia.

⤱ Adamite ⤱

Adamite from the Puttapa Zinc Deposit, South Australia.

⤱ Adamite ⤱

Cuprian adamite from the Kintore Open Cut, Broken Hill, New South Wales.

⤱ Acanthite ⤱

Acanthite from the Magnet Mine near Waratah, Tasmania. Photo width 2mm. Brian Carney specimen.