Op-Ed: Understanding LCT pegmatites - why context can make or break a lithium project

In the modern critical minerals rush, lithium-cesium-tantalum (LCT) pegmatites have taken centre stage as governments look to carve out a share of a market still dominated by brines. But as capital continues to flow into hard-rock lithium projects across Western Australia, Canada, and Africa, there is a recurring theme: how much of this momentum is backed by real geological context.  

If history tells us anything, it’s what happens when developers rush to mine without understanding the ore first. We need look no further than Magnum Mining’s Buena Vista project in Nevada. Although not an LCT pegmatite, it is a painfully fresh example of the impact that poor mineralogical understanding can have on processing behaviour, turning a promising asset into an operational headache. 

To understand this properly, it’s useful to recognise that LCT pegmatites are, by their very nature, highly zoned ore bodies. As these massive rock bodies form, they are constantly inundated by cycles of heat and fluids, continuously changing the mineral makeup in swirls, layers, and distinct pockets. Just as a multi-coloured ball of play-dough has a completely different colour in the centre than it does at the edge, the rock you drill at Section A is almost never identical to the rock you process at Section B.

A basic drill assay checks for total lithium the same way a lab checks that ball of play-dough for total weight. It gives you an overall average, but tells you nothing about the physical texture. It can’t tell you whether that lithium is locked inside a clean, heavy spodumene crystal that your gravity circuit can easily catch, or trapped in a mushy pocket of mica and fine alteration that will blind your processing screens and float right out into the tailings pile. 

When project developers rush past this fundamental reality, the result is a model that treats the orebody as a homogenous blob of rock. Whilst this looks good in the headlines and undeniably creates funding enthusiasm, it comes at a price.  

Case 1 – Mount Marion: the pitfalls of unmodeled mineralogy 

Fortunately, we don’t have to guess what that price is, Western Australia’s Mount Marion deposit provides a textbook example. While the plant used a hybrid Dense Media Separation (DMS) and flotation circuit to catch variable grain sizes, the project suffered from a flawed mineralogical assumption regarding lithium distribution.  

As mining progressed, that assumption unravelled. Ore from different parts of the deposit contained unexpected zones of fine-grained spodumene and high mica content which fundamentally changed how the material behaved during processing. Because micas break down into platy flakes and alter the density of the heavy medium slurry, they dragged down concentrate grades and elevated impurities. The team was then forced into expensive retrofits and processing modifications just to meet commercial specifications. 

Case 2 – Tanco: the trap of “one-size-fits-all” processing 

Canada’s historic Tanco pegmatite in Manitoba offers another great example of why geological context matters more than lithium grade. For decades, operators relied on a rigid academic model, assuming that the bulk of Tanco’s lithium mineralisation occurred purely as a massive spodumene-quartz Intergrowth. Under this assumption, they expected a highly uniform, predictable weight to volume ratio of roughly 60% spodumene to 40% quartz. 

That assumption was exposed in spectacular fashion. Because the model prioritised simple spodumene-quartz structures, they completely overlooked iron inclusions and phosphate minerals. Failing to account for the exact, granular mineral chemistry early on, acted as a massive financial drain and a technical bottleneck that eventually caught up with them, impacting the design efficiency of the processing plants and ultimately leading to shutdowns.  

Case 3 – Shaakichiuwaanaan: clues hiding in plain sight 

This brings us to modern flagship developments, most notably Patriot Battery Metals’ (PMET) Shaakichiuwaanaan project in Quebec, one of North America’s most significant and strategically vital hard-rock lithium discoveries.  

PMET’s Feasibility Study gets plenty right. It lays out a clean, detailed blueprint for site development, water management, and mining execution. However, there is an unusually heavy focus in its risk register on operational headwinds like permitting delays, labour availability, and logistics. This leaves an uneasy feeling, since, similar to the above-mentioned cases, there are several critical geological variables that are either left unaddressed or understated. Chief among them being actual rock composition. 

PMET’s own metallurgical test work acknowledges spikes in micas across the deposit, but whilst mineralogical characterisation was performed on 20 drill-core samples, those mineralogical variables are not carried forward into the 3D block model to predict plant performance across different pit domains. Instead, overall metallurgical recovery across the entire plant relies on a simplified 1D mathematical formula based strictly on total Li₂O head grade.  

Then there is a second, less obvious hint hiding in plain sight: Arsenic and Antimony. In the report, these elements are treated strictly as an annoying environmental waste nuisance to be isolated in stockpiles. What this approach misses is the geological reason they are there in the first place.  Metasomatic fluids don’t just transport arsenic and antimony along the edges of a deposit. Those exact same volatile, late-stage fluids are a primary cause of spodumene breakdown. They chemically destroy pristine, coarse spodumene crystals, degrading them into low-density clays, micas, and fine-grained intergrowths.  

In short, high arsenic and antimony levels are a clear indication that areas of this orebody will have higher amounts of clays present. Wherever you see a spike in arsenic, you are likely looking at a zone where primary spodumene has been degraded. By failing to model these elements in 3D across the deposit, management hasn’t just left an environmental question mark open, they have blinded themselves to where the Dense Media Separation plant’s lithium recovery will underperform inside the pit. High-arsenic blocks are most likely going to be lower-recovery blocks. 

The bottom line for developers and investors 

The long-term viability of any mineral project rests on our ability to learn. Tanco ultimately became an industry benchmark, not because it avoided complexity, but because operators learned to embrace it, mapping the deposit in three dimensions, separating the ore by geological domain, and matching processing strategies to the actual mineralogy of each zone. 

These cases should not be read as anomalies, nor as a triumph of our own misguided ability to avoid risk, but rather as a warning. No matter how large the organisation, or “assured” the investment, a project cannot survive without simple geological understanding.  

Nicholas Vafeas is the founder and director of BluMelt Mineral Consulting Limited, an independent consultancy specialising in geological assurance, critical minerals and investment de-risking.