DIAMOND CORE SAMPLING ERROR AND IMPLICATION TO RESERVE

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

DIAMOND CORE SAMPLING ERROR AND IMPLICATION TO RESERVE

Kusuma, Nusa^'
'Dept. Geology, PT Newmont Nusa Tengara

ABSTRACT

Sampling is one of significant factor to determine an economic of a deposit. Batu Hijau is one of largest porphyry disseminated and vein control copper gold deposit. Sampling performed during exploration to development periods contribute a bias. The bias occurred due to the nature of deposit, drilling and sampling technique.

The significant economic mineral occurred as dissemination, vein control or along the fracture as fracture filling. The usage of excessive water during drilling washed the economic mineral. Manual carelessly sampling results the economic minerals is not sampled. Those factors results the bias in resource and reserve estimation.

An improvement of sampling and drilling technique is developed based on grade bias study. The new technique prove to reduce the bias significantly.

Mineralogical type, lithological characteristics combine by recorded geotechnical parameters is investigated to quantify the bias. The developed bias adjustment formula is a function of lithology, grade and RQD.

Validation of developed bias adjustment through production shows the bias adjustment is valid to be implemented for resource and reserve estimation. The grade bias adjustment factor implemented to the block model estimation increase metal content which worth to one year production.