It's one of those how long is a piece of string questions, with...

It's one of those how long is a piece of string questions, with many variables: actual mineral concentration, scale, depth, landscape, location, availability of technology, capital intensity... 

In the global history of mining we've moved from the rare high grade supergene deposits with obvious outcrops in the early days to low grade deposits often hidden under the surface, while prospecting and beneficiation technology has had to keep pace with the growing demand for metals. Naturally the average grade of finds declines over time, so the mining investor's tolerance for lower grades has had to increase.

Many of the most profitable mines in the world are low grade, large scale. While the profit per unit is far lower, and resources consumed in production far greater, the scale of throughput can be immense, and the scale of output is what the world needs. The modern mine is typically massive, and produces a shitton of waste along with finished commodities. For instance, Bingham Canyon mine: 647Mt at 0.477% copper, 0.18g/t gold, 0.034% molybdenum and 2.1g/t silver. That's 210 tons of stuff for each ton of copper. Rio Tinto expects to produce over $20B of copper from it. 

Very few cobalt deposits have been found recently that are in that 1% range. Every deposit may have small sections of good ore that reach that figure though. Grade needs to be measured against scale, depth, capital intensity etc. Laterite deposits have various benefits: easy to prospect, are shallow and wide, often are free digging, and can have sections of higher grade material. There are many around in Australian especially because of the expense of developing them. The cobalt price is what is driving interest, as the nickel price has been destroyed in recent years by cheap Asian "nickel pig iron", which is only used for low-tech purposes. The downside is of course the now infamous HPAL beneficiation, which has huge capital cost. Not all laterites need HPAL: Australia and Africa have some deposits I know of that are relatively cobalt rich and easy to leach. 

Sulphide deposits are the retailer investor's holy grail, but real cobalt sulphide minerals are scarce and seem to usually appear as accessory metals in a replacement form - where hydrothermal waters and other processes have exchanged cobalt with, for instance, iron, producing low grade cobaltian pyrite. These deposits are generally regarded as copper or nickel mines with cobalt credits. High grade sulphides are the special but rare linnaeite and cattierite, which appear in small amounts in nickel and copper hydrothermal veins. Sulphides are less capital intense and less costly to process, as a rule of thumb, but scale determines capex to an extent, with some low-grade projects featuring similar capex to smaller laterites.

Cobalt also appears as arsenides; common examples are cobaltite, skutterudite, glaucodot, and the famous Moroccan erythrite (which is an oxidized concentrate form that appears on exposed minerals). The natural areas around Cobalt Camp are still contaminated with arsenic from the cowboy days 100 years ago. These days arsenide mining is carefully managed, and arsenic is also sold as a by-product.

So there's no absolute grading of grades... peer analysis can offer guides to who has the best in a group. In ground value can also give a clue as to the economic viability of a deposit, but that needs to be measured against expected capex and opex. 0.1% Co may not sound great, but at 100Mt, contains 100Kt cobalt worth $5.5B. It's a question of how much it costs to produce. An equivalent deposit at 1% Co would be 10Mt, which would be a rare wonder indeed. More likely, high grade deposits will be measured in Kt, like the 58Kt @ 0.51% Co deposit at Werner Lake, for an IGV of $16M. Some primary cobalt minerals occur with gold. These will become interesting in Cobalt Wave 2.

All base metals aren't doing too well atm though, except zinc, and perhaps copper, which may be showing signs of a recovery.