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Cragg Mine

Producer in Queensland, Australia with commodity Gemstone
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Host and associated rocks
  8. Nearby scientific data
  9. Geologic structures
  10. Ore body information
  11. Controls for ore emplacement
  12. Economic information about the deposit and operations
  13. Mining district
  14. Land status
  15. Ownership information
  16. Workings at the site
  17. Links to other databases
  18. Bibliographic references
  19. General comments
  20. Reporter information

Geologic information

Identification information

Deposit ID 10110084
MRDS ID TC34459
Record type Site
Current site name Cragg Mine

Geographic coordinates

Geographic coordinates: 142.6988, -23.12995 (WGS84)
Elevation 150
Relative position 175 KM SW OF THE TOWN OF WINTON

Site location context

Political divisions (FIPS codes)

Queensland(province)

Australia(country)

Australia(continent)

Land(continent)

Geographic areas

Country State
Australia Queensland

Comments on the location information

  • MINING LEASE NO. 17 CONSISTING OF TWO CLAIMS OF 100 SQ. M EACH

Commodities

Commodity Importance
Gemstone Primary

Comments on the commodity information

  • SOME NONGEM OPAL MAY BE INTERLAYERED; IRONSTONE MATRIX COMMON; RED AND GREEN DOMINANT PHENOMENAL COLOR BUT ALSO SHOWS BLUE.

Materials information

Materials Type of material
Hematite Gangue
Limonite Gangue

Analytical data

Result DUPLEX II REFRACTOMETER WITH MONOCHROMATIC LIGHT SOURCE IN 1.42-1.43 RANGE
Result LITTLE SHRINKAGE AND CRACKING
Result 2% OF MATERIAL DETACHES FROM MATRIX BACKING
Result HIGH DURABILITY
Result INERT TO LONG- AND SHORT-WAVE ULTRAVIOLET RADIATION

Host and associated rocks

  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Mudstone
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Siltstone
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Sandstone
    Rock unit name Winton Formation;
    Rock description Winton Formation;

Nearby scientific data

(1) 142.6988, -23.12995
ListMap

Economic information

Geologic structures

Type of structure Regional
Structure description Great Artesian Basin

Ore body information

  • General form STRATAFORM

Controls for ore emplacement

  • Fractures In Ironstone Concretions; Sandstone/Clay Interface And Rarely In Fractures In Petrified Wood.

Comments on the geologic information

  • DEPOSIT OCCURRENCE IN FERRUGINOUS ZONE OF WINTON FORMATION AT BOTTOM OF 100 M MORNEY WEATHERED PROFILE (50-70 MY OLD) WITH SUPERINPOSED CANAWAY WEATHERED PROFILE (25 MY OLD) WHICH IS SUGGESTED TO HAVE RELEASED SILICA FOR OPAL DEVELOPMENT; WINTON FORMATION COVERS AN AREA OF 700,000 SQUARE KM.

Economic information about the deposit and operations

Development status Producer
Commodity type Non-metallic
Deposit size Small
Significant No
Discovery year 1888
Discoverer Fred Cragg

Mining district

District name Winton District

Land status

Ownership category Private

Ownership information

  • Type Owner-Operator
    Owner Fred Cragg

Workings at the site

  • Type of workings Surface
    Overall depth 20M

Comments on the workings information

  • OPEN-CUT MINING INVOLVING NO MORE THAN 3 WORKERS USING BULLDOZER; OPERATIONS LIKELY INTERRUPTED BY MONSOON RAIN USUALLY FROM JANUARY THROUGH MARCH

Comments on development

  • TRUCK-MOUNTED AUGER DRILLS 75 CM IN DIAMETER, 20 M DEEP; GEOBOTANICAL INDICATORS INCLUDE MALLEEBUSH TREES AND LAPINGA TREES; NEW DEVELOPMENT EXTENSION OF 1880'S WORKINGS. ; ECON.COM: HAUL ABOUT 2 HOURS OVER UNIMPROVED ROAD REQUIRING 4-WHEEL DRIVE VEHICLE FOLLOWED BY 2 HOURS OVER TWO-LANE GRAVEL ROAD; OPAL PRODUCTION IS VERTICALLY INTEGRATED WITH IN-HOUSE CUTTING FACILITIES PLUS OWN WHOLESALE AND RETAIL OPERATIONS.

Reference information

Bibliographic references

  • Analytical Data

    WISE, W.R., 1993.

  • Deposit

    WISE, R.W., 1993, QUEENSLAND BOULDER OPAL: GEMS AND GEMOLOGY, V. 29, NO. 1, P. 4-15

General comments

Subject category Comment text
Deposit SEMI-ARID CLIMATE
Deposit SEAMS (4-5 MM THICK, UP TO 25 CM) AND POCKETS IN IRONSTONE CONCRETION (UP TO 30 CM IN DIAMETER), CALLED BOULDER OPAL (APPROX. 90%); ALSO SANDSTONE (1.5%) IRONSTONE MATRIX OR BAND OPAL (1.5%) AND PIPE OPAL (0.5%); LARGEST PIECE FOUND TO DATE WAS BANDED OPAL APPROXIMATELY 1 M X 60 CM X 25 CM; SOME UPPER SURFACES OF OPAL HAVE ROUNDED BOTRYOIDAL TEXTURES.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JUN-1993 Bliss, James D. U.S. Geological Survey

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

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