| Chapter 1 - Exploration Geology and Ore Reserves |
| Number |
Topic |
Rule of Thumb |
| 1.01 |
Discovery |
It takes 25,000 claims staked to find 500 worth diamond drilling to find one mine. Source: Lorne Ames |
| 1.02 |
Discovery |
On average, the time between discovery and actual start of construction of a base metal mine is 10 years; it is less for a precious metal mine. Source: J.P. Albers |
| 1.03 |
Discovery |
On average, the time between discovery and actual start of production of a mine in an established mining district (“brown field”) is seven years. Source: Sylvain Paradis |
| 1.04 |
Discovery |
On average, the time between discovery and actual start of production of a mine in a district where there is no previously established mining activity (“green field”) is ten years. Source: Sylvain Paradis |
| 1.05 |
Costs |
The amount expended on diamond drilling and exploration development for the purposes of measuring a mineral resource should approximately equal 2% of the gross value of the metals in the deposit. Source: Joe Gerden |
| 1.06 |
Bulk Sample |
The minimum size of a bulk sample, when required for a proposed major open pit mine is in the order of 50,000 tons (with a pilot mill on site). For a proposed underground mine, it is typically only 5,000 tons. Source: Jack de la Vergne |
| 1.07 |
Ore Reserve Estimate |
The value reported for the specific gravity (SG) of an ore sample on a metallurgical test report is approximately 20% higher than the correct value to be employed in the resource tonnage calculation. Source: Jack de la Vergne |
| 1.08 |
Ore Resource Estimate |
To determine an “inferred” or “possible” resource, it is practice to assume that the ore will extend to a distance at least equal to half the strike length at the bottom of measured reserves. Another rule is that the largest horizontal cross section of an ore body is half way between its top and bottom. Source: H. E. McKinstry |
| 1.09 |
Ore Resource Estimate |
In the base metal mines of Peru and the Canadian Shield, often a zonal mineralogy is found indicating depth. At the top of the ore body sphalerite and galena predominate. Near mid-depth, chalcopyrite becomes significant and pyrite appears. At the bottom, pyrite, and magnetite displace the ore. Source: H. E. McKinstry |
| 1.10 |
Ore Resource Estimate |
Archean aged quartz veins are generally two times as long as their depth extent, but gold zones within these vein systems are 1/5 - 1/10 as long as their depth extent. Source: Gord Yule |
| 1.11 |
Ore Resource Estimate |
In gold mines, the amount of silver that accompanies the gold may be an indicator of depth. Shallow gold deposits usually have relatively high silver content while those that run deep have hardly any. Source: James B. Redpath |
| 1.12 |
Ore Resource Estimate |
As a rule of thumb, I use that 2P (Probable) reserves are only such when drill spacing does not exceed five to seven smallest mining units (SMU). Open pit mining on 15m benches could have an SMU of 15m by 15m by 15m. Underground, an SMU would be say 3m by 3m by 3m (a drift round). Source: René Marion |
| 1.13 |
Ore Resource Estimate |
Your thumb pressed on a 200-scale map covers 100,000 tons of ore per bench (height assumed to be 50 feet). Source: Janet Flinn |
| 1.14 |
Strike and Dip |
The convention for establishing strike and dip is always the Right Hand Rule. With right hand palm up, open and extended, point the thumb in the down-dip direction and the fingertips provide the strike direction. Source: Mike Neumann |