Mining grade converter
This converter takes the grades you see in mining news releases and turns them into the units you'd rather read: grams per tonne, ounces per ton, ppm or percent. It also turns rare earth oxide grades into metal and checks the true width of a drill intercept.
How do you convert grams per tonne to ounces per ton?
Divide the g/t figure by 34.2857. You'll run into ounces per ton in older reports and US filings, while Canadian companies mostly report grams per tonne, so a 1980s drill log and a news release from last week can look like they disagree when they don't. The number comes from two definitions published by the US National Institute of Standards and Technology: a troy ounce is 31.1034768 grams, and a short ton is 2,000 pounds, or 0.90718474 tonnes.
Grams per tonne and ppm are the same thing for a grade by weight. A tonne is a million grams, so a gram in every tonne is one part per million. Copper and nickel are usually quoted in percent instead, and 1% is 10,000 ppm.
How do you convert a rare earth oxide grade to metal?
Multiply by the share of the oxide that's metal. Rare earth companies quote grades as oxides like Nd2O3, because that's how the elements are assayed and sold. But oxygen makes up part of every oxide, so the metal grade is always lower than the headline. The factors below come from the standard atomic weights set by the Commission on Isotopic Abundances and Atomic Weights.
| Oxide | Name | Metal share (factor) | 1% oxide equals |
|---|---|---|---|
| La2O3 | Lanthanum oxide | 0.8527 | 0.853% La |
| CeO2 | Cerium oxide | 0.8141 | 0.814% Ce |
| Pr6O11 | Praseodymium oxide | 0.8277 | 0.828% Pr |
| Nd2O3 | Neodymium oxide | 0.8574 | 0.857% Nd |
| Sm2O3 | Samarium oxide | 0.8624 | 0.862% Sm |
| Tb4O7 | Terbium oxide | 0.8502 | 0.850% Tb |
| Dy2O3 | Dysprosium oxide | 0.8713 | 0.871% Dy |
| Y2O3 | Yttrium oxide | 0.7874 | 0.787% Y |
| U3O8 | Uranium oxide | 0.8480 | 0.848% U |
| Li2O | Lithium oxide | 0.4645 | 0.465% Li |
Lithium carbonate equivalent (LCE) is 2.473 times the Li2O figure. Factors use CIAAW abridged atomic weights and are rounded.
That's also why a total rare earth oxide (TREO) grade always looks bigger than the metal you'd end up with. Our guide How to Read a Rare Earth Resource Estimate explains TREO, and What Is NdPr Oxide? covers the product most rare earth miners actually sell.
How do you work out true width from core length?
Multiply the core length by the sine of the angle between the drill hole and the vein. If the hole hits the vein square on, at 90 degrees, the core length is the true width. Come in at 30 degrees and you get twice as much core as the vein is thick.
That's how a long, exciting intercept can turn out to be a thin vein drilled at a slant. Canada's disclosure rule, NI 43-101, makes companies report true widths of the mineralized zone where they know them. This calculator assumes a straight hole and a flat zone, so use it as a sanity check, not a survey. How to Read Drill Results covers what else to look for.
Mining grade converter: frequently asked questions
How do you convert g/t to oz/t?
Divide by 34.2857. That's how many grams per tonne make one troy ounce per short ton, since a troy ounce is 31.1034768 grams and a short ton is 0.90718474 tonnes. A 5 g/t gold result is about 0.146 oz/t.
Is ppm the same as grams per tonne?
Yes, when the grade is measured by weight. A tonne is a million grams, so one gram in a tonne is one part per million. And 1% is 10,000 ppm.
How do you convert Nd2O3 to neodymium?
Multiply by 0.857. About 85.7% of neodymium oxide's weight is neodymium; the rest is oxygen. The table on this page gives the same factor for every common rare earth oxide.
What is lithium carbonate equivalent (LCE)?
It's lithium content expressed as the lithium carbonate it could make. To go from Li2O to LCE, multiply by about 2.473, the ratio of the two compounds' molecular weights.
How do you calculate true width from core length?
Multiply the core length by the sine of the angle between the hole and the vein. Ten metres of core cut at 30 degrees is only about 5.0 metres thick. That assumes a straight hole and a flat zone, so treat it as a rough check.