Field Guide
Mineral Exploration 101
A plain-English guide to how mineral exploration actually works — drilling, core logging, sampling, assays, and geophysics — written for geologists, students, and anyone reading drill results.
New articles published every Tuesday and Thursday.
Exploration Fundamentals
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What Is Mineral Exploration? The Process, Stage by Stage
Mineral exploration is the staged search for economically viable mineral deposits — from area selection and surveys through drilling to resource definition. Here's how each stage works, what it costs, and why most prospects never become mines.
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Exploration Methods Explained: Mapping, Geochemistry, Geophysics & Drilling
The four core mineral exploration methods are geological mapping, geochemical sampling, geophysical surveys, and drilling. Here's what each one detects, what it costs, and how they work together as a funnel from wide-area search to a drilled discovery.
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How Ore Deposits Form (and the Main Types)
Ore deposits form when geological processes concentrate metals far above their normal crustal abundance, through magmatic crystallisation, hydrothermal fluid flow, or surface weathering and sedimentation. Here's how each process works and the deposit types it produces.
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Geochemical Sampling: Soil, Stream Sediment & Rock Chip
Geochemical sampling is the practice of collecting soil, stream sediment, or rock chip samples across a target area and analysing them for trace-element concentrations that point toward buried or hidden mineralisation. Here's how each sample medium works, when to use it, and how geologists tell a real anomaly from background noise.
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Geophysical Surveys Explained: Magnetics, IP, EM, Gravity
Geophysical surveys map physical properties of the subsurface — magnetism, electrical chargeability, conductivity, and density — to find rock and mineralisation patterns invisible at surface. Here's how magnetic, IP, EM, and gravity surveys each work, what they're best at detecting, and how geologists read their results.
Drilling & Core
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Exploration Drilling Methods Compared (Diamond, RC, RAB, Auger, Sonic)
Diamond, RC, RAB, auger, and sonic drilling trade cost against sample quality and depth. Here's how each method works, what it samples, what it costs, and when explorers use it.
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Diamond Drilling Explained
Diamond drilling cuts an intact cylinder of rock — the core — with a diamond bit. Here's how the bit, core barrel, and wireline system work, and what core costs.
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RC (Reverse Circulation) Drilling Explained
RC drilling uses a downhole hammer and dual-wall rods to pulverise rock and blow the chips back up an inner tube. Here's how the hammer, cyclone, and splitter work, and where RC fits against RAB and diamond.
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Drill Core Sizes: BQ, NQ, HQ, PQ and What They Mean
BQ, NQ, HQ, and PQ are the standard diamond core sizes used in mineral exploration, running from roughly 37 mm to 85 mm in core diameter. Here's what the letters mean, how the sizes compare, and how to choose one.
Core Logging
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How to Log Drill Core, Step by Step
Logging drill core means recording everything the core reveals at measured depths, in a fixed sequence. Here's the field procedure, step by step — from depth-checking the core to validating the data.
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Lithology Logging: Identifying & Recording Rock Types in Drill Core
Lithology logging is the systematic depth-by-depth identification and description of rock types in drill core. Here's what every interval should capture — rock name, grain size, texture, colour, mineralogy, and contact type — and why getting it right matters.
Sampling & Assay
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Core Sampling & Splitting: Half-Core, Quartering & Why It Matters
Core sampling is the process of dividing drill core into representative pieces and sending one portion to the laboratory for assay. Here's how to split core correctly, choose sample intervals, and avoid the mistakes that compromise your data.
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How Assays Work: Fire Assay, ICP, XRF & Screen Fire
An assay is a laboratory measurement of the concentration of a target metal in a rock sample. Fire assay, ICP, XRF, and screen fire assay are the four methods you will encounter most often in mineral exploration — here is how each works, when to use it, and what its limitations are.
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How to Read Assay Results
An assay result is a grade number attached to a depth interval in a drill hole. This guide explains every column in a laboratory return file, how to composite samples into intercepts, what cut-off grade means, true width versus downhole width, metal equivalents, and what your QAQC data is telling you.
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How to Read a Drill-Result Press Release (Grade, Width, True Thickness)
A drill-result press release contains everything you need to evaluate a mineral discovery — if you know what to look for. This guide walks through every section of a typical announcement: the headline intercept, the results table, grade, width, true thickness, gram-meters, cut-off grade, depth context, and the red flags that reveal selective reporting.