Core drilling in mineral exploration: what a drill core can show
What drill core is, how it differs from drill cuttings, and which records help check exploration drilling results for an area in Kazakhstan.
Updated 29 September 2026 · 4 min read
Contents
Core drilling produces a drill core: a cylinder of rock taken from a borehole. It helps geologists study rocks at depth, their sequence and their features. But a box of core does not yet tell you how much metal an area contains. You also need to know the depth each sample came from, see the geological description, and review the sampling and assay results.
This guide is for people reviewing exploration materials for an area in Kazakhstan or preparing to discuss further work. It explains the terms and helps you ask a geologist useful questions. It deals with mineral exploration; choosing a water-supply well is a different task.
What is drill core, and how does it differ from cuttings?
In core drilling, the tool brings up rock as a cylindrical sample. Preserved core lets a geologist study how the rocks change with depth. The US Geological Survey (USGS) explains its purpose in these terms.
Drill cuttings are small fragments of broken rock brought out of a borehole during drilling. They also provide geological information, but preserve less detail of the rock's structure than core. The choice of drilling method depends on the question and the conditions in the area. There is no single method for every project.
What to look for in drilling records
A core photograph is useful when you know which borehole and depth interval it shows. Table 1 of the 2012 JORC Code covers drilling method, sample recovery, logging, sampling and assay quality. For an initial discussion, it helps to gather the following:
| Material | What it helps you check |
|---|---|
| Borehole plan with coordinates and coordinate reference system | Where the work took place and whether it concerns the area of interest |
| Borehole depth, inclination and direction | How the hole crossed the rocks being studied |
| Logging records and photographs labelled with borehole numbers and intervals | What the geologist observed and the depth to which each record relates |
| Core recovery data | How much material was recovered from each drilled interval |
| Sample register and laboratory reports | How the samples, intervals and assay results connect |
| Analytical methods and quality-control records | How the reported numbers were checked |
This is a starting list, not a complete review programme. JORC is used here as a reference for questions about data. Its table does not turn these materials into a JORC report or set mandatory rules for every project in Kazakhstan.
Why core recovery matters
Core recovery shows how much of a drilled interval is represented by the recovered core. If some rock was lost, the geologist must assess how that loss affects the description and whether the samples are representative. Loss may affect different kinds of material unevenly, so the percentage cannot be judged apart from the rock and sampling conditions.
In particular, JORC calls for checking whether sample recovery may be related to the grade of the mineral or metal of interest. This guide does not set one “adequate percentage” for every task. That judgment requires a review of the particular materials.
Can a drill core show whether there is gold?
A geological description helps identify intervals of interest. Determining gold grade requires suitable sampling and assays with quality control. The colour of a rock or shiny grains visible in a photograph do not, by themselves, establish metal grade.
Even a strong result from one sample cannot be applied to an entire area. You need to understand the sampled interval's position and length, the surrounding results and the geological setting. Our separate guide explains the differences between exploration results, resources and reserves.
There is another important question: the length of an intersection along a borehole may differ from the true width of the mineralised body. If the body's geometry is unknown, an interval length must not automatically be called its thickness.
What to prepare before discussing new work
First state your goal: test a specific geological idea, clarify the area's geology or understand older results. Then gather the maps, reports and information on earlier boreholes that you have, and list what is missing. The geological materials review checklist may help.
In your first message, it is enough to give the region, the goal and a list of available materials. Depths, the number of boreholes, the drilling method and the sampling plan should be discussed in light of the source data. A single price per metre does not describe the full scope of geological work. Ask separately what a proposal includes, how samples will be documented and what results will be delivered to the client.
Rights to work in the area are a separate question. The exploration licence guide provides a starting point.
Discuss the source materials with QAZNEDR
You can begin with: “Hello! I found you on qaznedr.kz. I need advice on exploration drilling data for an area in [region].” The team will clarify the task and what data you have. Terms for sharing documents will be agreed separately.
Contact us through WhatsApp or WeChat. For more on working with geological information, see the geological services page.