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Yinnietharra Dravite mine (South Open Cut), Tomkap tourmaline mines (Soklich), Yinnietharra (Yinnietharra Station; Yinnetharra), Upper Gascoyne Shire, Western Australia, Australiai
Regional Level Types
Yinnietharra Dravite mine (South Open Cut)Mine
Tomkap tourmaline mines (Soklich)Group of Mines
Yinnietharra (Yinnietharra Station; Yinnetharra)- not defined -
Upper Gascoyne ShireShire
Western AustraliaState
AustraliaCountry

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Key
Latitude & Longitude (WGS84):
24° 34' 22'' South , 116° 10' 33'' East
Latitude & Longitude (decimal):
Locality type:
Köppen climate type:


A well-known locality for very large and well-formed dark brown dravite crystals. The deposit was discovered in 1918. A. Soklich claimed the mining lease and started mining in 1968. During the initial period of mining (January 1969 to January 1971) more than 12 tons of dravite crystals were produced for specimens. More recently (2010) the mineral lease has been taken up by Tom Kapitany, who renamed it Tomkap tourmaline mine, produced more specimens and provided some of the following information.

It consists of two pits 1km apart roughly parallel on strike north-north west. Brown dravite occurs at the south pit, and black dravite in the north pit.

The dravite is found in a phlogopite-plagioclase schist on Morrissey Hill in the Gascoyne Province of the Precambrian Shield of Western Australia (Bridge et al., 1977). Associated pegmatites cut across strike of the tourmaline-bearing schists. Regional metamorphism and deformation of metasediments with highly hydrothermally altered zones allowed tourmaline crystals to form in the mica schists, possibly with boron derived from underlying pegmatites. Dravite rarely has associated apatite crystals up to 125mm. Dravite crystals up to 7kg have been found. There are different zones existing in 2 contact zones producing smaller crystals and central zone producing giant dravites.

The main south deposit is about 5 meters wide and runs for a few hundred meters. The existing pit is about 30 meters long and had a very curious, friendly goanna living in there. The pit contains highly fluorescent chalcedony under both UV and short wavelengths, and exists in fracture lines to the surface.

Most of the brown dravite specimens on the market come from the Soklich mining period (1968-1971), with crystals found sporadically within pods. Near surface crystals were of poor quality due to fracturing, commonly encrusted by secondary opal and carbonates from weathering.

Better quality material occurs at 3-6 metres below the surface. The crystals appear opaque but have minor translucence, vitreous lustre, often indented with small booklets of mica (although most specimens on the market have these removed). Some of the specimens are very large, to a few kg. They occur as single and intergrown crystals. Plagioclase as poikilitic inclusions are commonly found in the dravites aligned as flattened laths sub-parallel to the principal axes of the dravite crystals. Inclusions can also include phlogopite, subhedral rutile, apatite, zircon and fluorite.

Crystal forms present include a hexagonal prism, trigonal prism, and rhombohedral terminations. There was initial confusion amongst collectors, as crystals are almost equidimensional, or equant, with short prismatic zones terminated by rhombohedra, superficially resembling the dodecahedral morphology of garnets.

Fetherston, J.M., Stocklmayer, S.M., Stocklmayer, V.C. (2017) Gemstones of Western Australia, second edition. Geological Survey of Western Australia, Mineral Resources Bulletin 25, 356 pages, it is reported that:

"At the Yinnetharra North deposit, 1.5 km to the north of the Yinnetharra dravite openpit, schorl or black tourmaline was originally reported. In more recent years, it has been established that all tourmaline in this area is black dravite, with an MgO content of 9.85%. The Yinnetharra North deposit, on former mineral claim MC09/215, is in a black phlogopite schist containing large, euhedral black dravite rhombohedra, many with double terminations and internal zoning visible in thin section. Maximum crystal size is recorded as 60 mm in diameter and 23 cm in length".

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Standard Detailed Strunz Dana Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


5 valid minerals.

Detailed Mineral List:

'Albite-Anorthite Series'
Reference: Bridge, P. J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
'Apatite'
Formula: Ca5(PO4)3(Cl/F/OH)
Colour: green
Description: in lumps to 10 cm and small crystals
Reference: Bridge, P. J. , Daniels, J. L. & Pryce, M. W. (1977): The dravite crystal bonanza of Yinnietharra, Western Australia. Mineralogical Record 8 (2): 109-111
Dravite
Formula: Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
Habit: hexagonal prism, with a trigonal prism and terminated by the rhombohedron
Colour: golden brown
Description: Largest crystal about 11,5 kg (Bridge et al. 1977). The dravite measures from 1 to 15 cm in length. Equidimensional dodecahedral crystals can be confused with garnets.
Reference: Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
Fluorite
Formula: CaF2
Description: As inclusions in dravite
Reference: Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
'Mica Group'
Reference: Jordi Fabre
'Monazite'
Description: Found in phlogopite
Reference: Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
Opal
Formula: SiO2 · nH2O
Reference: Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
Rutile
Formula: TiO2
Reference: Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
Zircon
Formula: Zr(SiO4)
Description: As inclusions in dravite
Reference: Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The dravite crystal bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.

List of minerals arranged by Strunz 10th Edition classification

Group 3 - Halides
Fluorite3.AB.25CaF2
Group 4 - Oxides and Hydroxides
Opal4.DA.10SiO2 · nH2O
Rutile4.DB.05TiO2
Group 9 - Silicates
Dravite9.CK.05Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
Zircon9.AD.30Zr(SiO4)
Unclassified Minerals, Rocks, etc.
'Albite-Anorthite Series'-
'Apatite'-Ca5(PO4)3(Cl/F/OH)
'Mica Group'-
'Monazite'-

List of minerals arranged by Dana 8th Edition classification

Group 4 - SIMPLE OXIDES
AX2
Rutile4.4.1.1TiO2
Group 9 - NORMAL HALIDES
AX2
Fluorite9.2.1.1CaF2
Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in >[6] coordination
Zircon51.5.2.1Zr(SiO4)
Group 61 - CYCLOSILICATES Six-Membered Rings
Six-Membered Rings with borate groups
Dravite61.3.1.9Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with H2O and organics
Opal75.2.1.1SiO2 · nH2O
Unclassified Minerals, Mixtures, etc.
'Albite-Anorthite Series'-
'Apatite'-Ca5(PO4)3(Cl/F/OH)
'Mica Group'-
'Monazite'-

List of minerals for each chemical element

HHydrogen
H DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
H ApatiteCa5(PO4)3(Cl/F/OH)
H OpalSiO2 · nH2O
BBoron
B DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
OOxygen
O DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
O ApatiteCa5(PO4)3(Cl/F/OH)
O ZirconZr(SiO4)
O OpalSiO2 · nH2O
O RutileTiO2
FFluorine
F ApatiteCa5(PO4)3(Cl/F/OH)
F FluoriteCaF2
NaSodium
Na DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
MgMagnesium
Mg DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
AlAluminium
Al DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
SiSilicon
Si DraviteNa(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
Si ZirconZr(SiO4)
Si OpalSiO2 · nH2O
PPhosphorus
P ApatiteCa5(PO4)3(Cl/F/OH)
ClChlorine
Cl ApatiteCa5(PO4)3(Cl/F/OH)
CaCalcium
Ca ApatiteCa5(PO4)3(Cl/F/OH)
Ca FluoriteCaF2
TiTitanium
Ti RutileTiO2
ZrZirconium
Zr ZirconZr(SiO4)

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Bridge, P.J., Daniels, J.L., Pryce, M.W. (1977) The Dravite Crystal Bonanza of Yinnietharra, Western Australia. The Mineralogical Record, 8(2), 109-111.
Tom Kapitany, pers comm.
Fetherston, J.M., Stocklmayer, S.M., Stocklmayer, V.C. (2013) Gemstones of Western Australia. Geological Survey of Western Australia, Mineral Resources Bulletin 25, 306 pages.

Other Regions, Features and Areas containg this locality

Australia
Australian PlateTectonic Plate

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