Built by a geologist

Lithological Logging

Accurate lithological logging forms the foundation of geological interpretation. Consistent, detailed descriptions enable correlation between holes and construction of geological models. Systematic Lithology Description For each lithological unit, describe in order : 1. Rock Name Use a standardized naming convention: - Grain size + Composition + Rock Type - Examples: "Fine-grained biotite granite", "Massive chlorite schist" 2. Color - Fresh vs. weathered color - Use standard color charts if available - Primary and secondary colors 3. Grain Size | Category | Size Range | Description | |----------|------------|-------------| | Fine | <1mm | Individual grains not visible | | Medium | 1-5mm | Grains visible, <pencil lead | | Coarse | 5-30mm | Clearly visible crystals | | Very Coarse | 30mm | Pegmatitic | 4. Texture - Equigranular, porphyritic, glomeroporphyritic - Massive, foliated, layered - Vesicular, amygdaloidal 5. Mineralogy - Essential minerals define rock name - Accessory minerals - Estimate modal percentages - Note crystal form and alteration 6. Structure - Foliation, lineation, banding - Veining type, intensity, orientation - Brecciation, shearing Contact Logging Contact Types - Sharp : Distinct boundary <1cm - Gradational : Progressive change note width - Intrusive : Igneous into country rock - Faulted : Structural contact Information to Record - Exact depth - Contact type - Alpha angle - Nature of contact knife-sharp, irregular, etc. - Evidence of movement Coding Systems Most companies use standardized codes: Lithology Codes examples - GRN = Granite - BAS = Basalt - AND = Andesite - SST = Sandstone - SLT = Siltite - MST = Mudstone/Shale - LST = Limestone - SKN = Skarn - QTV = Quartz Vein Benefits - Faster logging - Database compatibility - Consistent between loggers - Statistical analysis Always use your company/project's standard code list!