Key points
- Sphalerite is a zinc sulfide mineral that occurs in many different ore deposit types and locations in Australia and globally.
- Zinc is on the US critical minerals list and is important across many technologies from galvanized steel to solar photovoltaic panels and battery storage.
- Sphalerite can also accommodate other elements in its crystal structure including several on Australia’s critical minerals list.
Sphalerite is a very cool mineral. It is a beautiful, complex and diverse zinc sulfide (ZnS) mineral that also hosts a treasure trove of other critical elements. These include manganese, cadmium, mercury, indium, thallium, gallium, germanium, antimony, tin, lead, silver and cobalt.
It is the main mineral resource of zinc. While not on Australia’s critical mineral list yet, zinc is on the US critical minerals list and is important across many technologies, from galvanized steel to solar photovoltaic panels and battery storage.
Sphalerite occurs in many different ore deposit types, from sedimentary deposits to ancient volcanic regions, and new ores forming on the modern sea floor. It has even been found in meteorites originating from the formation of the solar nebula about 4.5 billion years ago.
Prized as gemstones by some, sphalerite comes in an array of colours. From colorless to deep brown, the spectrum of colour reflects other elements in its crystal structure. It is this quality of sphalerite to accommodate so many other elements that is gaining attention.
Studying sphalerite is helping geologists understand more about ore-forming fluid processes, and opening up ways to extract more value from mineral resources to unlock these critical materials.
Untapped potential of sphalerite byproducts
The untapped potential of sphalerite is an example of how mineral processing and extraction often focuses on one or two elements of interest. This ignores other potential valuable components present in the minerals and the ores.
In the past, it has been more cost-effective to focus mineral processing activities on main commodities rather than fully understand and characterise whole ores for other potential value.
Consequently, many of our important, strategic and critical elements may be currently residing above ground in low-grade resources such as tailings and rock piles.
Many historic sites may have extracted only one to two percent of the ore, leaving 98 percent of it as readily available, precrushed, above-ground, underutilized, new potential value.
That is where my work comes in: I’m visiting CSIRO from Cornell University for six months as the Fulbright Australia-US Chair in Science, Technology and Innovation applying my field of geomet to environmental, social and governance (ESG) activities. Geomet links geological information with engineering and downstream impacts to reduce risk, create opportunities for sustainable mineral resource development, and engage local communities to be economically empowered.
Engineering more value from potential resources
Some zinc mines have sphalerite crystals that can be metres in size, that contain significant amounts of cadmium, germanium, indium and gallium.
Some smelters have significant germanium slag resources from processing zinc ores, as well as tellurium from coexisting copper minerals. These elements are important for electronics, semiconductors, and solar energy technologies.
My work links the full characterisation of materials to better designed, less wasteful mineral resources practices. It opens the door for value to be reclaimed from historical slag heaps and mining byproducts and embeds ESG into future resource recovery campaigns.
I believe it is our responsibility as geologists to not only understand the geology, but also to use that knowledge to ensure that the whole minerals value chain carefully works to gain the full value of the materials to help all of our stakeholders
Linking up geology and engineering solutions improves resource recovery and reduces impacts on the environment.
Extraction of minerals from the earth brings them into circulation for humanity. We are just trying to maximise that value for the long term, continuing round and round in the ultimate circular system.
After all, as George Wetherill said, we are all made of stardust.