Module 5: Core Handling & Sampling Best Practices 

1. Proper Core Extraction and Labeling Techniques

Effective core extraction and systematic labeling form the foundation of reliable geological data collection. These processes require meticulous attention to detail from the moment the core reaches the surface.

Core Extraction Protocol:

• Controlled Removal from Barrel:

• Use core catchers or split tubes to prevent sample loss during extraction

• For fragile cores, employ freezing techniques (dry ice or liquid nitrogen) to maintain integrity

• Orientation Preservation:

• Mark top/bottom of core before removal using scribe lines or orientation tools

• Record facing direction in inclined holes using downhole survey data

• Fractured Core Handling:

• Place in custom trays with foam inserts to maintain original positioning

• Photograph in situ before attempting reconstruction

Labeling Standards:

• Primary Identification:

• Waterproof tags with: Project ID, Hole Number, Run Number, Depth Interval

• Barcode/RFID tags for digital tracking systems

• Secondary Marking:

• Direct rock marking with permanent ink pens (alcohol-based for wet cores)

• Color-coded system for different lithologies

• Digital Documentation:

• Tablet-based logging with GPS-stamped photos

• QR code system linking physical samples to database records

2. Core Logging Fundamentals

Systematic core logging transforms raw samples into actionable geological data through standardized documentation procedures.

Logging Hierarchy:

1. Initial Assessment:

• RQD (Rock Quality Designation) measurement

• Basic lithology and major structure identification

2. Detailed Logging:

• Mineralization contacts with millimeter precision

• Structural measurements (dip, strike, fault characteristics)

3. Specialized Analysis:

• Alteration mineralogy (hand lens or portable XRD)

• Vein density and morphology documentation

Logging Tools & Techniques:

• Essential Toolkit:

• Geological compass with clinometer

• UV light for carbonate/fluorite detection

• Acid bottle for carbonate testing

• Digital Enhancements:

• Hyperspectral scanning for rapid mineral identification

• 3D photogrammetry for virtual core analysis

• Data Recording:

• Standardized forms (adapted to project needs)

• Digital logging software with dropdown menus for consistency

3. Sample Preservation and Contamination Prevention

Maintaining sample integrity requires proactive measures throughout the handling chain to ensure analytical validity.

Preservation Methods by Sample Type:

• Geochemical Samples:

• Double-bagged in chemically inert plastic

• Refrigeration for organic-rich samples

• Geotechnical Samples:

• Wax sealing for moisture retention

• Specialized core liners for sensitive clays

• Microscopy Samples:

• Argon-flushed containers for sulfide preservation

• Dark storage for light-sensitive minerals

Contamination Control Matrix:

4. Quality Control in Sample Collection

Implementing rigorous QC protocols ensures data reliability from field to laboratory.

QC Framework Components:

• Field Duplicates:

• 1 duplicate per 20 samples (5% rate)

• Collected as split core or adjacent material

• Standards & Blanks:

• Certified reference materials inserted blind

• Blank samples using sterilized quartz

• Chain of Custody:

• Tamper-evident sample bags

• Digital tracking with timestamps

• Dual-signature transport manifests

Common Pitfalls & Solutions:

• Depth Discrepancies:

• Laser-measured core length verification

• Magnetic collar sensors for exact positioning

• Sample Bias:

• Randomized selection for assay splits

• Whole-core analysis for critical intervals

• Database Errors:

• Automated field validation rules

• Triple-check protocol for manual entries

Integrated Core Management Workflow

1. Extraction: Oriented removal with minimal disturbance

2. Stabilization: Immediate preservation per sample type

3. Documentation: High-resolution imaging + physical logging

4. Subsampling: Clean protocols for different analyses

5. Storage: Climate-controlled with access tracking

6. Dispatch: Secure shipment with custody documentation

Best Practice Tip: Implement a "sample lifecycle" tracking system that follows each specimen from drilling through final analysis, with automated alerts for any handling deviations.