This episode of GeOCHemISTea explores cobalt cycling, critical metals, and why geochemists need to think beyond bulk chemistry to understand how elements behave in surface environments. Sam is joined by Owen Missen, lecturer in environmental geology at the University of Tasmania and researcher with CODES, whose work focuses on the environmental geochemistry and mineralogy of elements like cobalt and tellurium.

The conversation explores why cobalt matters in modern technology, how nanoscale particles are changing the way we think about metal mobility, and what this means for environmental risk around mine waste and legacy sites. Owen also shares insights from Tasmania’s mining legacy, including the Mount Lyell–Macquarie Harbour system, and reflects on why understanding metals at the right scale matters for better mining and environmental decisions.

For this episode we read:

Natural cobalt–manganese oxide nanoparticles: speciation, detection and implications for cobalt cycling (Missen et al., 2024)

Simon Bolster joins GeOCHemISTea to unpack what actuallymakes near-surface geochemistry work in mineral exploration: understanding regolith and landforms before you ever “put dirt in bags.” With four decades in gold exploration, Simon argues that many programs fail not because geochemistry is “bad,” but because sampling and analytical choices do not match the terrain,the cover, or the project stage.

The conversation moves from regolith terrain assessment andmapping as the real starting point, to why “lowest detection limit” is not a substitute for good planning. Simon also breaks down industry “silver bullets” (MMI, calcrete, ultrafines) and why blanket adoption creates false confidence. Finally, he explains how DetectOre upgrades gold from ppb-scale field chemistry into something actionable and fast, by leaching and concentrating gold onto a collector device that can be read by pXRF, enabling real-time decision-making while rigs are still turning.

For this episode we read:

Valuing time and how some of the latest technologies arecompressing time to fast track and de-risk new discoveries and mines (Bolster, 2025)

In this episode of GeOCHemISTea, host Sam Scher engages in a thought-provoking conversation with Professor Mohsen Yahyaei, a mineral processing engineer and director at the Julius Kruttschnitt Mineral Research Center. They explore the impact of geographical differences on mental health, particularly how varying daylight hours can affect mood and productivity. The discussion transitions into the importance of integrating geological and processing data to optimize mineral extraction processes, emphasizing the need for collaboration between geologists and processing engineers to enhance decision-making and reduce waste in mining operations.

As the conversation unfolds, Mohsen shares his journey from mining exploration to mineral processing, highlighting the significance of automation and AI in modern mining practices. He advocates for a holistic approach to mining that considers the entire lifecycle of minerals, from extraction to recycling, and stresses the importance of leveraging existing geological data to improve processing efficiency. The episode concludes with a forward-looking perspective on the future of mining, envisioning a fully integrated system that not only maximizes resource extraction but also prioritizes environmental sustainability and circular economy principles.

In this episode of GeOCHemISTea, Sam talks with Mike Stock, Professor at Trinity College Dublin, about magma systems from eruption to emplacement. Drawing on work in the Galápagos and Ireland, Mike explores how the same geochemical and petrological processes govern both volcanic activity and ore formation.

The conversation focuses on breaking down silos between volcanology and economic geology—highlighting shared tools, concepts, and models that are often studied in isolation. The episode closes with a discussion on batholiths and crustal-scale magma systems, offering a fresh perspective on how modern volcanology can inform interpretations of ancient intrusions and mineralized systems, making it relevant for volcanologists and economic geologists alike.

For this episode we read:Integrated Petrological and Geophysical Constraints on Magma System Architecture in the Western Galápagos Archipelago: Insights From Wolf Volcano (Stock et al., 2018)

Late-stage volatile saturation as a potential trigger for explosive volcanic eruptions (Stock et al., 2016)

Cryptic evolved melts beneath monotonous basaltic shield volcanoes in the Galápagos Archipelago (Stock et al., 2020)

This month on GeOCHemISTea, Sam sits down with Scott Halley to talk about extracting meaningful mineralogy from standard four-acid assay data. Scott walks through how the classic MINSQ approach evolved into modern linear-programming methods that handle solid solutions, honor thermodynamics, and produce fast, first-pass mineralogy models.

They also dig into ambiguity in geologic interpretation, “cognitive entrenchment” in porphyry systems, and how linking calculated mineralogy to rock physics is helping bridge the gap between geochemistry and geophysics.

For this episode we read: MINSQ - a least squares spreadsheet method for calculating mineral proportions from whole rock major element analyses (Herrmann and Berry, 2002)

Alecos Demetriades, applied geochemist and Chair of the IUGS Commission on Global Geochemical Baselines (2024–2028), joins GeOCHemISTea to unpack the Global Geochemical Reference Network (GGRN): why a 160×160 km grid matters, how harmonized sampling/analysis underpins trustworthy baselines, and what QA/QC must look like before interpretation.

We touch on FOREGS, leveling national datasets to global references, and practical ways exploration and mining teams can access, use, and contribute to these datasets.

Plus: tea stories during Tea Time and why passing knowledge to the next generation keeps this global effort moving. For this episode we read: ⁠International Union of Geological Sciences Manual of Standard Methods for Establishing the Global Geochemical Reference Network⁠

This month on GeOCHemISTea, we welcome back Simon Griffiths, Principal Consultant at Third Planet Exploration Services, to unpack the geochemical exploration strategies for low-sulfidation epithermal systems. From vein textures to vanadium-rich roscoelite halos, Simon walks us through practical strategies for geochemical targeting and alteration mapping. He shares insights into sampling, spectral workflows, and how roscoelite at Porgera became one of the most reliable vectors to high-grade gold. Plus a wild tale about how an ICP machine was used to crack down on gold theft in the mine lab.

For this episode we read:Geology of the Porgera Gold Deposit, Papua New Guinea (Hay et al., 2020)

In this episode of GeOCHemISTea, we're joined by Hugh De Souza to explore the evolution of gold analysis; from 4,000-year-old fire assay traditions to disruptive technologies like photon assay. With over 40 years at research and industry analytical labs and deep experience in mineralogy, geochemistry, and lab innovation, Hugh shares his unconventional path into analytical geochemistry, breaks down the physics behind modern methods, and reflects on what the future holds for gold assay. Whether you're a field geo or into analytical chemistry, this one's for you.