what core bit size is used for mineral exploration

Selecting the right core bit size is one of the most critical decisions in any mineral exploration program. The diameter you choose directly affects core recovery quality, drilling cost per meter, rig capacity requirements, and the amount of sample material available for laboratory analysis. This guide covers the standard wireline sizes used in mineral exploration worldwide and explains how to match each size to your project's specific needs.

Standard Wireline Core Bit Sizes for Mineral Exploration

The mining and exploration industry uses a standardized wireline core barrel system with five primary sizes: AQ, BQ, NQ, HQ, and PQ. Each size corresponds to a specific hole diameter and core diameter, allowing interchangeable components across different manufacturers. The table below summarizes the standard dimensions:

NQ: The Industry Standard for Most Mineral Exploration

NQ is the most widely used core bit size in mineral exploration programs across the globe. The 47.6 mm core diameter provides enough sample material for geochemical assays, petrographic analysis, and basic geotechnical testing while keeping drilling costs manageable. NQ bits are compatible with a wide range of drilling rigs, from portable units to large truck-mounted systems, making them the go-to choice for most greenfield and brownfield exploration projects.

TY Drilling Bits offers a comprehensive range of NQ-size impregnated core bit options designed specifically for hard rock mineral exploration. The impregnated diamond matrix ensures consistent penetration rates in granite, basalt, and other abrasive formations commonly encountered during exploration drilling.

HQ: When You Need Larger Samples for Detailed Analysis

HQ core bits produce a 63.5 mm diameter core, making them the preferred choice when the exploration program requires more sample material for comprehensive laboratory testing. The larger core diameter is particularly valuable for:

• Metallurgical test work — larger samples provide sufficient material for flotation, leaching, and comminution tests
• Structural geology studies — wider cores preserve delicate structural features such as veins, fractures, and foliation planes
• Resource definition drilling — higher core recovery in fractured or weathered zones compared to smaller diameters
• Multi-element geochemistry — enough material for multiple assay pulps and quality control duplicates

For programs transitioning from exploration to resource definition, stepping up from NQ to HQ can significantly improve the confidence level of geological models and resource estimates. TY Drilling Bits supplies HQ-sized surface set core bit options that deliver excellent core recovery in medium to hard formations, with smooth core surfaces ideal for structural logging.

PQ: Maximum Core for Bulk Sampling and Deep Exploration

PQ is the largest standard wireline size, producing an 85 mm diameter core. This size is typically reserved for bulk sampling campaigns, very deep exploration holes (over 1,000 meters), and projects where orebody geometry requires large-diameter samples for accurate grade estimation. The trade-off is higher operational cost — PQ drilling requires larger rigs with greater torque and pullback capacity, consumes more drilling fluid, and generates more cuttings that need disposal.

BQ: Lightweight Option for Reconnaissance and Narrow-Vein Targets

BQ bits drill a 60 mm hole and recover a 36.5 mm core. This smaller size is well-suited for preliminary reconnaissance drilling, narrow-vein gold or silver exploration, and projects in remote locations where helicopter-supported or man-portable rigs are required. The smaller hole diameter reduces rig size requirements, fuel consumption, and water usage — all significant advantages in logistically challenging terrains.

AQ: Shallow Investigation and Environmental Baseline Studies

AQ is the smallest commonly used wireline size, recovering a 27 mm core from a 48 mm hole. It is primarily used for shallow geotechnical investigation, environmental baseline sampling, and sterilisation drilling around planned infrastructure. While AQ cores are too small for most metallurgical testing, they provide sufficient material for geochemical analysis and basic rock quality designation (RQD) measurements.

Matching Core Bit Type to Geological Conditions

Size alone is not enough — the type of core bit must match the rock formation being drilled. Below is a guide to selecting the right bit type for common mineral exploration scenarios:

How to Choose the Right Core Bit Size for Your Project

Selecting the optimal core bit size requires balancing several factors. Here is a practical decision framework:

• Define your analytical requirements first. Consult with your laboratory to determine the minimum sample mass needed for assays, metallurgical tests, and any specialized analyses. If the program requires petrographic thin sections, geotechnical strength testing, and multi-element geochemistry, HQ or larger is recommended.
• Assess the geological conditions. In highly fractured or weathered zones, larger diameters generally achieve better core recovery. If the orebody is known to have narrow, high-grade veins, NQ can be sufficient for grade estimation while reducing costs.
• Evaluate rig capacity and logistics. PQ drilling requires larger rigs with higher torque and pullback capacity, while NQ can be handled by smaller, more portable rigs. Factor in site access, water availability, and fuel logistics when choosing a size.
• Consider the drilling depth. Deeper holes generate higher torque and require more robust drill string components. HQ and PQ are common for holes exceeding 500 meters, where the larger diameter provides better hole stability and core recovery at depth.
• Calculate the cost per meter. Larger sizes cost more per meter drilled, but the cost per gram of recovered sample may actually be lower. For example, HQ produces roughly 1.8 times more core volume than NQ, while the per-meter drilling cost increase is proportionally smaller, making HQ more cost-effective on a per-sample basis when extensive testing is required.

Sourcing Quality Core Bits for Mineral Exploration

The quality of your core bits directly impacts core recovery, drilling efficiency, and ultimately the reliability of your exploration data. When evaluating suppliers, look for manufacturers with:

• ISO 9001 certification — ensures consistent quality control in manufacturing processes
• Full size range availability — a supplier that stocks AQ through PQ sizes can support your program as it evolves
• Custom matrix formulation — the ability to adjust diamond concentration and matrix hardness for specific geological conditions
• Export experience — suppliers with established international logistics can reliably deliver to remote project sites
• Competitive lead times — 15 working days or less is a reasonable benchmark for standard sizes

TY Drilling Bits, based in Xi'an, China, manufactures a complete range of diamond core bits for mineral exploration, including electroplated, impregnated, TSP, and surface set designs. With over a decade of manufacturing experience and more than 90% of production exported to international markets, the company provides reliable quality at competitive prices across all standard wireline sizes from AQ to PQ.