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Boulder Main Reef Gold Mine (Great Boulder Main Reef; Boulder South Extended), Golden Mile Mines, Kalgoorlie-Boulder, Kalgoorlie-Boulder Shire, Western Australia, Australia

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Latitude & Longitude (WGS84): 30° 47' 49'' South , 121° 30' 19'' East
Latitude & Longitude (decimal): -30.79705,121.50529
GeoHash:G#: qdw2uct6n
Locality type:Mine
Köppen climate type:BSh : Hot semi-arid (steppe) climate

The Boulder Main Reef was a historic lease at the southern end of the Golden Mile. With the Great Boulder Proprietary lode traversing the lease it was a rich mine in the early days. The Chaffers lease bordered it to the west, Great Boulder East lease to the east, and Great Boulder Proprietary to the north.

The original prospector was H.G. Parsons, the mine named Boulder South Extended. He sold the lease in 1895 to a company floated in London called the Great Boulder Main Reef Gold Mining Company. This company was registered on 23 August 1895, with 30 000 pounds working capital. Three shafts were initially sunk, although the one in the south-west corner of the property was soon abandoned. Bainbridge Seymour and Co were the initial consulting engineers, and thirty men had been employed on the lease.

M. Modest Maryanski discovered telluride on the dump in 1896, significantly increasing the value of the mine. An inspection of the underground workings revealed a vein dipping slightly east, with a distinct Hanging Wall in schistose diorite country rock. The vein was largely calcite, dark greenish quartz and dark greenish talc matter (as described by Maryanski), throughout heavily impregnated with pyrite and telluride of gold.

Previously this ore had been sent to the mill, which was not able to process it, and was left on the dumps to be used as a road metal base. The mine was at the forefront investigating the best ways to process the telluride ores, and by 1900 had a new Diehl processing plant. The lease also contained a normal 10 head battery.

While this was a rich mine and dividends were paid, by 1909 they were struggling to find payable ore lodes. The mine was closed for much of this year, the plant leased to the Chaffers mine for six months. The Chaffers company then decided to purchase the lease in 1910, and the Great Boulder Main Reef Co went into liquidation.

Commodity List

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

Mineral List

17 valid minerals.

Rock Types Recorded

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Alphabetical List Tree Diagram

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

0 - 2.588 Ma

ID: 742372
colluvium 38491

Age: Pleistocene (0 - 2.588 Ma)

Description: Colluvium and/or residual deposits, sheetwash, talus, scree; boulder, gravel, sand; may include minor alluvial or sand plain deposits, local calcrete and reworked laterite

Comments: regolith; synthesis of multiple published descriptions

Lithology: Regolith

Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia). [5]

Neoarchean - Mesoarchean
2500 - 3200 Ma

ID: 3187518
Archean volcanic rocks

Age: Archean (2500 - 3200 Ma)

Comments: Yilgarn Craton

Lithology: Greenstone belt; mafic-ultramafic volcanic rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Southern Times newspaper (Bunbury) (1895), Boulder South Extended Mine, 30/11/1895
The West Australian newspaper (Perth) (1895), Boulder South Extended Mine- to the Ed., 29/11/1895
Kalgoorlie Western Argus newspaper (1896), The Boulder Main Reef. Telluride Discovery, 26/11/1898
Kalgoorlie Western Argus newspaper (1896), Boulder Main Reef Telluride Discovery- to the Ed., 26/11/1896
Kalgoorlie Miner newspaper (1898), Great Boulder Main Reef, 29/01/1898
The Register newspaper (Adelaide) (1909), Great Boulder Main Reef, 05/08/1909
The Register newspaper (Adelaide) (1910), Chaffers and Boulder Main Reef, 27/01/1910
The Sydney Morning Herald newspaper (1896), Great Boulder Main Reef, 29/12/1896
Kalgoorlie Miner newspaper (1900), Boulder Main Reef, 18/06/1900
Simpson, E.S. (1948), Minerals of Western Australia, Vol 1, 2, & 3, State Government of Western Australia, 1948

Mineral and/or Locality  
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