<% FROM="\InformationForInvestors\AnnualReport98\pages\resource.htm" SITE="anglogold-main" %> Mineral resources

 

 

Mineral resources

 

AngloGold has adopted internationally accepted mineral resource classification standards, which are broadly aligned with the Australian Code for Reporting Identified Mineral Resources and Ore Reserves as well as with the latest draft of the South African Code for Reporting of Mineral Resources and Mineral Reserves. This approach has been adopted both for clarity of reporting to shareholders and for facilitating ore body management by the company.

space60.gif (56 bytes)This system is a strictly confidence-based resource categorisation and estimation procedure. The mineral resource is sub-divided into areas of greater or lesser confidence in the estimate, ultimately based both on the geo-statistical characteristics of the ore body and on the proximity, type and amount of geological and sampling data that might have been used to extrapolate values into particular blocks. Different geo-statistical techniques are applied as appropriate and the quality of the estimates is tested by cross-validation and reconciliation.

space60.gif (56 bytes)Owing to differences in the definition of resources and reserves, the mineral resources segment has been divided into four separate sections:

block_m.jpg (1943 bytes) South African operations
block_m.jpg (1943 bytes) Other African operations
block_m.jpg (1943 bytes) American operations
block_m.jpg (1943 bytes) Ergo

 

Abridged definitions
Mineral resource:
a mineral deposit that may eventually be economically and legally extracted. Mineral resources reported in this document are restricted to the portion included in the life of mine plan and are sub-divided into:

space60.gif (56 bytes) Inferred mineral resource: a mineral resource where sampling and other data are insufficient to permit interpretation of the geological framework or to enable prediction of the continuity of mineralisation with any degree of confidence.

Indicated mineral resource: the spacing of sampling and geological data points affords a degree of confidence high enough to give a reasonable indication of continuity of mineralisation.

Measured mineral resource: the sampling and geological data points are spaced such that continuity of geological character and grade may be estimated with a high degree of confidence.

Mineral reserve: that part of a mineral resource which could be technically, economically and legally mined under conditions existing at the time of reporting.

Mineral reserve (South African operations): reflects the payable component of the mineral resource as calculated under conditions pertaining in December 1998. It should be noted that these conditions will change and therefore pay limits will change in the future. In addition, the long-range mining plan will mine a mixture of 'payable reserve' and 'marginal resource'. Mineral reserves are sub-divided into:

Probable mineral reserve: that part of the indicated mineral resource above a pay limit calculated in December 1998.

Proved mineral reserve: that part of the measured mineral resource above a pay limit calculated in December 1998.

The tonnages quoted as reserves and/or resources are in situ and are estimated over a stoping width. Grades are also in situ and estimated over a stoping width with no allowance being made for additional dilution or gold loss.

It follows from these definitions that there are components of the mineral deposit that are unlikely to be economically and legally extracted in the foreseeable future and which are therefore not reported as part of the mineral resource.

space60.gif (56 bytes) Mineral reserve (Other African operations): reflects the estimated tonnage and grade as delivered to the treatment facility and includes allowances made for additional dilution or gold loss.

Mineral reserve (Ergo): reflects the estimated tonnage and grade of the mineral resource in the slimes dams and sand dumps, or portions thereof, that are currently technically and economically treatable.

Total mineral reserves ? (proved plus probable)


Metric

Imperial


Contained Contained
Tonnes Grade gold Tons Grade gold
million g/t tonnes million oz/t million oz

South African operations † 1998 204,8 17,03 3 488,5 225.6 0.497 112.1
1997 211,0 17,08 3 603,2 232.8 0.498 116.0

Other African operations** 1998 15,3 3,06 46,8 16.9 0.089 1.5
1997 17,7 3,10 54,9 19.5 0.092 1.8

American operations** 1998 140,8 2,08 292,5 155.3 0.061 9.4
1997 ? ? ? ? ? ?

Ergo 1998 206,2 0,39 79,8 227.3 0.011 2.6
1997 256,1 0,39 99,7 282.3 0.011 3.2

Total 1998 567,1 6,89 3 907,6 625.1 0.201 125.6
?1997 484,8 7,75 3 757,8 534.6 0.226 121.0

† Excludes Driefontein
** Reserves attributable to AngloGold

? Excludes American operations

Total mineral resources* ? (measured plus indicated)
* Includes proved and probable mineral reserves

Metric

Imperial


Contained Contained
Tonnes Grade gold Tons Grade gold
million g/t tonnes million oz/t million oz

South African operations † 1998 356,8 12,55 4 478,7 393.4 0.366 144.1
1997 389,1 12,66 4 924,9 429.1 0.368 158.1

Other African operations** 1998 39,2 2,35 92,3 43.2 0.068 2.9
1997 40,1 2,37 95,2 44.1 0.068 3.0

American operations** 1998 282,3 2,38 670,8 311.3 0.069 21.7
1997 ? ? ? ? ? ?

Ergo 1998 395,6 0,34 135,4 436.1 0.010 4.4
1997 441,1 0,34 151,5 486.2 0.010 4.9

Total 1998 1 073,9 5,01 5 377,2 1 184.0 0.146 173.1
?1997 870,3 5,94 5 171,6 959.4 0.173 166.0

† Excludes Driefontein
** Resources attributable to AngloGold

? Excludes American operations

space60.gif (56 bytes)
South African operations*

South African operations - Metric

South African operations - Imperial

*Excludes Driefontein

Other African operations

Other African operations - Metric

Other African operations - Imperial

space60.gif (56 bytes)
 

Reconciliation
The year on year reconciliation of the total mineral resource (measured plus indicated) is reflected below:

South African underground operations*


Metric

Imperial


Tonnes Contained gold Tons Contained gold
million tonnes million million oz

1997 389,1 4 924,9 429.1 158.1
Depletion ?13,2 ?199,3 ?14.7 ?6.5
Structure ?15,3 ?121,4 ?17.0 ?3.8
Transfers ?39,2 ?379,6 ?43.3 ?12.2
To/from LOM (+/-) ?24,8 ?394,5 ?27.3 ?12.7
Abandoned ?0,9 ?11,7 ?1.0 ?0.4
Adjustment 61,1 660,3 67.6 21.6
1998 356,8 4 478,7 393.4 144.1

* Excludes Driefontein

 

Other African operations


Metric

Imperial


Tonnes Contained gold Tons Contained gold
million tonnes million million oz

1997 76,5 196,8 84.3 6.3
Depletion ?6,1 ?17,7 ?6.7 ?0.6
Change in stockpile 0,5 1,3 0.6 0.0
Adjustment 4,5 11,4 4.9 0.4
1998 75,4 191,8 83.1 6.1

Life of mine milling potential

The estimated life of mine milling potential at a starting average gold price in January 1999 of R58 400 per kilogram or $298 per ounce with declining annual throughput is set out below. The estimate is based on data and assumptions which are continually being reviewed and milling potential could change significantly.


Metric Imperial

Milled Gold Estimated Milled Gold Estimated
tonnes Recovery prod. life tons Recovery prod. life
million g/t tonnes years million oz/t million oz years

South African
underground
1998 348,8 8,41 2 932,2 32 384.6 0.245 94.4 32
operations* 1997 387,0 8,22 3 180,6 33 426.6 0.240 102.2 33

Other African
operations
1998 35,9 3,19 114,5 7 39.6 0.093 3.7 7
1997 41,4 3,21 133,1 8 45.6 0.092 4.2 8

* Excludes Driefontein

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