Heavy Mineral Sands Ore Deposits - Grade and Tonnage Distribution

Grade and Tonnage Distribution

The grade of a typical heavy mineral sand ore deposit is usually low. Within the 21st century, the lowest cut-off grades of heavy minerals, as a total heavy mineral (THM) concentrate from the bulk sand, in most ore deposits of this type is around 1% heavy minerals, although several are higher grade.

Of this total heavy mineral concentrate (THM), the components are typically

• Zircon, from 1% of THM to upwards of 50% of THM,
• Ilmenite, generally of 10% to 60% of THM
• Rutile, from 5% to 25% of THM
• Leucoxene, from 1% to 10% of THM
• Trash minerals, typically quartz, magnetite, garnet, chromite and kyanite, which usually account for the remaining bulk of the THM content
• Slimes, typically minerals as above and heavy clay minerals, too fine to be economically extracted.

Generally, as zircon is the most valuable component and a critical ore component, high-zircon sands are the most valuable. Thereafter, rutile, leucoxene and then ilmenite in terms of value given to the ore. As a generality, typically the valuable components of the THM concentrate rarely exceed 30%.

Being ancient stranded dune systems, the tonnage of most deposits is in excess of several tens of millions of tonnes to several hundred million tonnes. For example, the medium-sized Coburn mineral sands deposit, Western Australia, is 230 million tonnes at 1.1% heavy minerals, and is 13km long.