The key is how easy the lithium can be removed from the lattice of the ore, so its is a difficult question to answer in the now, but at a guess would want your grades to be over 1.3% Li20 if it is lepidolite IMO, but that is just a guess as haven't taken much notice of lepidolite in the past. Noting right now lithium prices are quite high so as deleterious elements flow into costs then in a way what is economic actually depends on lithium prices in the future, a natural point, and lithium shortfalls mean higher prices and more diversification of potential lithium resource suppliers as well.
With spodumene, if you have a coarse grains and low deleterious elements you can use DMS, DMS/foatation or floatation to achieve 6% quality specs for concentrate. Where it is fine grained and/or the lithium is difficult to remove from the lattice of the ore then you use flotation generally. As a general rule, floatation costs are higher than DMS, but you have higher recoveries in floatation as well, and also you may decide to use floatation in spodumene if you are aiming to make a product greater than say 6% concentrate.
Taking this to lepidolite, costs will be higher, assuming same grades as spodumene say both grade 1.2% Li20, because of higher deleterious elements in lepidolite as a general rule, and the likely need to use in effect a 'floatation' equivalent method of lithium extraction (ie. in effect what I am saying is not a base method of lithium extraction like DMS) to produce concentrate. Hence why grade is a key here if lepidolite, as extraction will have costs attached.
METs are the key here, as they give an indication as to i.) deleterious elements and 2.) how easy is it to liberate the lithium from the ore, which then flow through into costs. In terms of 2, if it is not easy to liberate it also means your likely to get more deleterious elements in the solution that you need to deal with when making 6% grade concentrate meaning higher costs as well.
By way of background, and I need to get to speed with lepidolite methods of extraction this post discusses DMS/floatation itself for spodumene - halfway down this post in a general thread I post in relating to lithium that some may find that thread useful around lithium -
Post #:54283727 .
Difficult question to answer, but suspect the market will be wanting above 1.3% Li20 if it is lepidolite, 1% minimum if it is spodumene. And obviously not just a few metres, want some decent hits whether it is spodumene or lepidolite. Market will trash EFE if say hit 2% spodumene but have only a 2 metre hit, but will rerateEFE if it hit 1.5% Li20 lepidolite in a 40 metre interval, an obvious point.
Too early to tell, so risk reward equation is high here, and free carry strategies this side of the market IMO are a key as well, but that is IMO.
If others have a view, please share as this is a learning forum and I haven't really looked at lepidolite before in terms of resource extraction methods and costs attached.
Posted enough
All IMO
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