How to Conduct a Mining Reconnaissance Survey in Uganda

A reconnaissance survey is the very first stage of mineral exploration — the broad, systematic search that determines whether a region or area of interest warrants further, more detailed investigation. It is the stage at which exploration companies cast their net wide, using relatively low-cost methods to scan large areas and identify the most promising targets for follow-up work. Done well, a reconnaissance survey saves enormous amounts of time and money by focusing subsequent exploration investment on areas with genuine mineral potential. Done poorly — or skipped entirely — it results in wasted drilling budgets, missed opportunities, and poorly informed investment decisions.

For Uganda, where vast geological terrains remain underexplored by modern standards, reconnaissance surveys are particularly important. The country's mineral potential is well documented in broad terms — gold in the greenstone belts, tin and wolfram in the western highlands, limestone and iron ore in the east, rare earths in several districts — but the specific locations, extents, and grades of most deposits remain poorly defined. Reconnaissance is the essential first step in unlocking that potential.

This guide explains what a reconnaissance survey is, when and why it is used, the methods employed, and how the results guide subsequent exploration decisions. We also draw on ALOM Mining & Geohydro Services' own reconnaissance work — including our limestone survey across Uganda for Hima Cement — to illustrate these principles in practice.

What is a Reconnaissance Survey?

A reconnaissance survey — sometimes called a preliminary survey or regional survey — is a broad-scale investigation designed to identify areas of potential mineralisation over a large geographic region. It is the earliest and least detailed stage of the mineral exploration process, sitting before prospect-level exploration, target drilling, and resource definition in the exploration pipeline.

The defining characteristics of a reconnaissance survey are:

Broad geographic scope: Reconnaissance typically covers hundreds or thousands of square kilometres, sometimes spanning entire geological provinces or districts.
Low to moderate cost per unit area: Methods are chosen for their ability to cover large areas efficiently rather than for high resolution or precision.
Objective of target identification: The goal is not to define a mineral resource but to identify areas (targets or anomalies) that justify more detailed and costly investigation.
Multi-disciplinary approach: Reconnaissance integrates remote sensing, geological observation, geochemical sampling, and literature review to build a regional picture.

In the context of Uganda's exploration sector, reconnaissance surveys are relevant for:

Mining companies acquiring new exploration licences and needing to prioritise their work areas
Investors evaluating regional mineral potential before committing to specific projects
Government geological surveys mapping and cataloguing the national mineral endowment
Industrial mineral consumers (such as cement companies) searching for raw material sources

When is a Reconnaissance Survey Used?

Reconnaissance is appropriate in the following situations:

New Exploration Licence Acquisition

When a company acquires an exploration licence covering a large area, a reconnaissance survey is the logical first step. The licence area may cover hundreds of square kilometres, and it is neither practical nor economically sensible to conduct detailed exploration across the entire area simultaneously. Reconnaissance allows the company to rapidly assess the entire licence, identify the most promising sectors, and concentrate detailed work where it will have the greatest impact.

Regional Mineral Assessment

Government geological surveys and international development organisations frequently commission reconnaissance surveys to assess the mineral potential of entire districts, regions, or geological belts. These regional assessments inform policy decisions, attract investment, and guide the allocation of exploration licences. Uganda's Department of Geological Survey and Mines (DGSM) has conducted various reconnaissance-level surveys over the decades, though coverage remains incomplete.

Industrial Mineral Sourcing

Companies seeking specific industrial minerals — such as limestone for cement manufacture, clay for brick production, or aggregate for construction — use reconnaissance surveys to identify and evaluate potential sources across a wide search area. This is precisely the context in which ALOM Mining & Geohydro Services conducted a reconnaissance limestone survey across multiple districts of Uganda for Hima Cement, systematically evaluating limestone occurrences to identify those most suitable for cement production.

Pre-Investment Screening

Investors considering entry into a particular mineral commodity or geographic region use reconnaissance-level information to screen opportunities and identify areas worthy of more detailed due diligence and investment.

Reconnaissance Survey Methods

A well-executed reconnaissance survey employs a suite of complementary methods, each contributing different types of information. The methods are deliberately chosen for their ability to cover large areas at reasonable cost.

1. Desktop Literature Review

Every reconnaissance survey begins with a thorough review of existing information. This includes:

Historical geological reports: Government geological survey bulletins, colonial-era geological reports, and previous exploration reports for the area of interest. Uganda has a rich archive of geological literature dating back to the early twentieth century, though some records are fragmented or difficult to access.
Academic publications: University research theses, journal articles, and conference papers on the regional geology.
Previous exploration data: Reports from companies that have previously held exploration licences in the area, including any geological, geochemical, or geophysical data they collected.
Mineral occurrence databases: Government and international databases (e.g., the DGSM mineral occurrence records, USGS, BGS) that catalogue known mineral showings.
Mining cadastre data: Review of current and historical mineral rights allocations to understand the exploration history and status of the area.

The desktop review serves to compile all existing knowledge into a coherent baseline, identify data gaps, and formulate initial hypotheses about where mineralisation might occur.

2. Satellite Imagery Analysis

Modern satellite imagery is one of the most powerful tools for reconnaissance-stage exploration. Freely available and commercial satellite datasets provide invaluable information about geology, structure, alteration, vegetation, and land use across vast areas.

Types of satellite data used in reconnaissance:

Optical imagery (Landsat, Sentinel-2, ASTER): Multispectral imagery that reveals rock types, soil types, vegetation patterns, and hydrothermal alteration zones through their spectral signatures. Certain mineral assemblages — such as iron oxides, clays, and carbonates — have distinctive spectral characteristics that can be detected and mapped remotely.
Radar imagery (Sentinel-1, ALOS PALSAR): Radar penetrates cloud cover and vegetation to reveal topographic and structural features. Particularly useful in Uganda's tropical environment where persistent cloud cover can limit optical imagery.
Digital elevation models (SRTM, ASTER GDEM): High-resolution topographic data that reveals geological structures (faults, lineaments, fold axes) through their expression in the landscape.
High-resolution commercial imagery (WorldView, Pleiades): Used for detailed examination of specific features identified in lower-resolution datasets.

Analytical techniques include:

Band ratio analysis to highlight specific mineral assemblages
Principal component analysis to enhance subtle spectral variations
Lineament mapping to identify structural features that may control mineralisation
Vegetation stress analysis — certain plants growing over mineralised ground may show distinctive spectral signatures due to elevated metal concentrations in the soil

3. Aerial Photography Interpretation

Where available, aerial photographs provide detailed views of the landscape that complement satellite imagery. In Uganda, extensive aerial photography coverage was acquired during the colonial era and in subsequent government survey programmes. Stereoscopic interpretation of aerial photographs allows geologists to:

Map geological contacts, faults, and folds in three dimensions
Identify outcrops, quarries, and historical mining workings
Assess vegetation and land use patterns that may relate to underlying geology
Plan access routes and logistics for field visits

While aerial photography is increasingly supplemented by drone surveys for site-specific work, the existing archive of photographs remains a valuable reconnaissance resource.

4. Regional Geological Map Review

Uganda is covered by a series of regional geological maps at scales of 1:250,000 and 1:100,000, produced by the Department of Geological Survey and Mines and, in some areas, by international geological surveys. These maps show the distribution of major rock types, geological structures, and known mineral occurrences.

During reconnaissance, these maps are used to:

Understand the regional geological framework and identify favourable geological settings for the target mineralisation
Locate known mineral occurrences and geological features of interest
Plan field visits to key geological exposures and mineral showings
Identify areas where the existing mapping may be outdated, inaccurate, or insufficient

For a detailed discussion of geological mapping methodology, see our geological mapping guide.

5. Field Reconnaissance Visits

After the desktop and remote sensing phases, field visits are conducted to ground-truth the remote interpretations, observe the geology first-hand, and collect samples. Reconnaissance field visits differ from detailed geological mapping in their broader scope and lower sampling density. The objective is not to produce a detailed map but to confirm the geological setting, verify features identified remotely, and collect representative samples.

During field reconnaissance, geologists typically:

Visit key outcrops and geological exposures to confirm rock types and structures
Examine historical mine workings, prospecting pits, and artisanal mining sites
Interview local communities and artisanal miners about mineral occurrences and mining history
Observe landscape features, drainage patterns, soil colours, and vegetation that may provide clues to underlying geology
Photograph and document observations systematically using GPS-referenced records

Field visits are essential because remote sensing and literature can only tell part of the story. There is no substitute for a trained geologist's direct observation of the rocks, structures, and landscape features in the field.

6. Rock Sampling

Rock sampling during reconnaissance involves collecting representative samples from outcrops, exposures, mine dumps, and other accessible locations. These samples are sent to accredited laboratories for analysis to determine their mineral content, metal grades, and geochemical characteristics.

Common types of rock samples collected during reconnaissance:

Grab samples: Selected pieces of rock collected from outcrops or mine dumps. Grab samples provide qualitative information about the types of mineralisation present but are inherently biased (geologists tend to sample the most interesting-looking material) and should not be used for resource estimation.
Float samples: Loose rocks found on the surface that have been transported from their original location by gravity, water, or human activity. Float samples indicate that mineralisation exists somewhere up-slope or up-stream but do not pinpoint its exact location.
Channel samples: Continuous samples cut across an outcrop or vein to provide a more representative grade estimate. Channel sampling is more systematic than grab sampling but is typically reserved for later stages of exploration.

7. Stream Sediment Sampling

Stream sediment sampling is one of the most effective and widely used reconnaissance geochemical methods. It exploits the fact that streams naturally sample and concentrate minerals and elements from their entire catchment area, providing a composite geochemical signature for the upstream terrain.

How stream sediment sampling works:

Fine-grained sediment is collected from the active stream bed at planned sample points, typically near stream confluences or at regular intervals along major drainages.
Samples are sieved in the field to a standard size fraction (commonly minus 80 mesh / 180 microns).
Samples are sent to an accredited laboratory for multi-element geochemical analysis.
The results are plotted on maps, and catchments with anomalously high concentrations of target elements are identified as areas of interest for follow-up.

Stream sediment sampling is particularly effective in Uganda's tropical environment, where thick soil cover and dense vegetation can make direct geological observation difficult. A well-designed stream sediment survey can rapidly identify areas of anomalous geochemistry across large areas at relatively low cost.

Design considerations include:

Sampling density: Typically one sample per 5–25 square kilometres at the reconnaissance stage
Sample medium: Fine-grained active stream sediment, or heavy mineral concentrates for specific target minerals
Analytical methods: Multi-element ICP-MS or ICP-OES analysis to screen for a broad suite of elements
Quality control: Duplicate samples, blanks, and standards to ensure data reliability

How Reconnaissance Guides Subsequent Exploration

The ultimate purpose of a reconnaissance survey is to make a decision: where should we explore next, and where should we not waste resources? The results of reconnaissance feed directly into the planning of the next exploration stage.

Target Ranking and Prioritisation

The reconnaissance data — geological observations, remote sensing interpretations, sample results, and literature analysis — are synthesised to produce a ranked list of targets. Each target is evaluated based on:

Geological favourability: Does the local geology match the expected setting for the target mineralisation?
Geochemical response: Did rock or stream sediment samples return anomalous values for target elements?
Structural setting: Is the target located on or near geological structures (faults, shear zones, contacts) that typically control mineralisation?
Remote sensing anomalies: Did satellite imagery or aerial photography reveal alteration zones, structural features, or other features of interest?
Historical evidence: Is there evidence of past mining, prospecting, or artisanal activity that confirms mineral presence?
Accessibility and logistics: Can the target be efficiently accessed for follow-up exploration?

Exploration Programme Design

Based on the target ranking, the exploration team designs a focused programme for the next stage — typically prospect-level geological mapping, systematic geochemical sampling, and ground geophysical surveys over the highest-priority targets. This focused approach ensures that the more expensive detailed exploration methods are applied only where the reconnaissance evidence justifies them.

Investment Decision Support

For investors and company management, the reconnaissance results provide the evidence base for decisions about whether to continue exploring a licence area, relinquish it, or seek joint venture partners to share the cost and risk of further work.

ALOM's Reconnaissance Experience: The Hima Cement Limestone Survey

ALOM Mining & Geohydro Services has extensive experience conducting reconnaissance surveys across Uganda. One notable example is our reconnaissance limestone survey conducted for Hima Cement, one of Uganda's leading cement manufacturers.

The objective was to identify and evaluate limestone occurrences across multiple districts of Uganda to secure future raw material supply for cement production. Our reconnaissance programme included:

Desktop compilation and review of all available geological literature and mineral occurrence records for limestone in Uganda
Satellite imagery interpretation to identify areas of carbonate rock exposure
Systematic field visits to limestone occurrences across the target districts
Rock sampling and laboratory analysis to determine calcium carbonate content, silica, alumina, and other quality parameters relevant to cement manufacture
Assessment of deposit size, accessibility, land tenure, and development potential for each occurrence
Ranking of occurrences based on quality, quantity, accessibility, and overall suitability for cement production

This programme efficiently narrowed a country-wide search to a shortlist of priority targets, enabling Hima Cement to focus its detailed evaluation and investment on the most promising sites.

Planning a Reconnaissance Survey in Uganda: Practical Considerations

Permitting

In Uganda, reconnaissance-level exploration activities — including geological mapping, sampling, and field visits — generally require a reconnaissance permit or an exploration licence from the Department of Geological Survey and Mines. The specific permit type depends on the nature and scale of the work.

Logistics

Uganda's road network has improved significantly but remains challenging in some mineral-rich areas, particularly in the Rwenzori foothills, Karamoja, and parts of the northern and southwestern districts. Field teams must plan for:

Vehicle access (4WD vehicles are essential in most exploration areas)
Accommodation (field camps may be necessary in remote areas)
Safety and health precautions (malaria, remote area risks)
Community engagement and permission to access land

Timing

Uganda has two rainy seasons (March–May and September–November) that can significantly affect field accessibility. Reconnaissance fieldwork is generally most efficiently conducted during the dry seasons (December–February and June–August), when roads are passable and outcrop exposure is maximised.

Cost

Reconnaissance is by design the most cost-effective stage of exploration. A well-planned reconnaissance programme covering a large licence area in Uganda might cost between USD 20,000 and USD 100,000, depending on the scope, methods, and duration — a fraction of what detailed exploration and drilling would cost for the same area.

Conclusion

The reconnaissance survey is the foundation upon which all subsequent exploration is built. It is the stage at which a vast search area is systematically narrowed to a manageable set of high-priority targets, each supported by multiple lines of evidence. Skipping or cutting corners on reconnaissance is a false economy that invariably leads to poorly directed exploration spending downstream.

For companies and investors entering Uganda's mineral exploration sector, a well-executed reconnaissance survey is the most efficient and cost-effective way to begin. It provides the geological intelligence needed to make informed decisions about where to invest further, and it demonstrates to stakeholders — including government regulators, joint venture partners, and financiers — that the exploration programme is being conducted with professional rigour.

ALOM Mining & Geohydro Services offers comprehensive reconnaissance survey services across Uganda, combining experienced field geologists, modern remote sensing capabilities, and deep local knowledge. From regional mineral assessments to commodity-specific sourcing surveys, our team delivers the geological intelligence that drives sound exploration investment. Contact us to discuss your reconnaissance survey requirements.