In geology and mining exploration, core angles (specifically alpha, beta, and gamma angles) are relative measurements used to determine the exact, real-world 3D orientation of geological structures—such as faults, veins, fractures, and bedding planes—found within a cylindrical drill core sample. Because a drill core is extracted from deep underground and rotates during drilling, geologists use specialized Core Orientation Tools to mark a reference line (usually the “bottom-of-hole” line) along the cylinder. The Three Core Angles
When a flat geological structure intersects a cylindrical drill core, it cuts it at an angle, creating an elliptical shape on the rock surface. Geologists define this intersection using three principal angles:
Alpha Angle (α): The acute angle measured between the central core axis and the long axis (the longest part) of the intersection ellipse. This angle ranges from 0° to 90°.
Beta Angle (β): The angle measured clockwise around the circumference of the core, starting from the oriented reference line to the furthest downhole point (apex) of the ellipse. It ranges from 0° to 360°.
Gamma Angle (γ): The angle measured directly on the planar surface itself between the long axis of the ellipse and a linear feature, such as a fault scratch lineation. Why Core Angles Matter
Subsurface Modeling: By combining alpha and beta measurements with the known path and tilt of the drill hole, software can convert relative core angles into Absolute True Compas Measurements (dip and azimuth).
Resource Mapping: Knowing the exact angle of structures tells mining companies where a gold or copper vein is heading next.
Mine Safety: Geotechnical engineers map out these fracture angles to predict structural weaknesses in rock, preventing mine collapses and wall failures. Stockholm Precision Tools Core Orientation in Mining Exploration | Methods & Tools
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