GRADE CONTROL ACTIVITIES, A METHOD TO DETERMINE Au-Ag GRADE IN TOGURACI GOLD PROJECT

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

GRADE CONTROL ACTIVITIES, A METHOD TO DETERMINE Au-Ag GRADE IN
TOGURACI GOLD PROJECT

Ewa F Rappe^'
'Mine Geology Department, PT. Nusa Halmahera Minerals
ABSTRACT

Toguraci is located in the North Maluku province of Eastern Indonesia, on the north arm of the island of Halmahera. It is a classic example of a volcanic-hosted, low-sulphidation, epithermal quartz vein deposit. Mining at Toguraci commenced in the last quarter of 2003 and has produced >180 KOz per annum since.

Grade control activities include 1:200 scale geologic trench mapping, face sampling, and reverse circulation drill hole sampling. Trench mapping (+/- sampling) is undertaken on each 5 meter bench, face sampling on each 2.5 meter bench, while reverse circulation drilling is completed at each 15 meters bench. Information gathered includes lithology, alteration, mineralization, structure, and quartz percentage which are stored digitally in MS Access and are run under SURPAC software. Data used for the compilations typically comprise over 21,300 m of reverse circulation drill data and 3,000 m of trench mapping data.

Reverse Circulation (RC) drill data is primarily used for reserve calculation for each 15 meter cut. This data is very good for reserve – resource comparison to improve Toguraci deposit model, better exploration understanding through adjacent area, and to help mine engineers to redesign pit boundary if necessary to obtain optimize stripping ratio. Trench, RC drill and face sample data are very crucial for Au-Ag determination.