Basalt lithology pattern

Angular marks marking a fine-grained lava.

Also known as: Basalt ornament, Extrusive igneous pattern, Lava rock pattern

Maps & navigationScientificStandard profile

Meanings

On a geological map a basalt is ornamented with fine angular marks, the standard pattern for a fine-grained extrusive igneous rock.

Officially standardisedVerified fact
Marks a basalt or similar fine-grained extrusive igneous rock.
Contexts: Maps
Officially standardisedVerified fact
Uses a finer ornament than granite, the density of the pattern following the grain size of the rock it stands for.
Contexts: Maps

A dense scatter of small angular marks and short strokes filling the rock unit.

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Geologic map
Wikipedia · retrieved 2026-08-24
Tertiary reference. Used for how a structural symbol is read and for the plain-language name of a feature. Structural definitions follow the cartographic standard.
FGDC Digital Cartographic Standard for Geologic Map Symbolization
United States Geological Survey for the Federal Geographic Data Committee · retrieved 2026-08-24
An openly published national standard defining geologic map symbols, lithologic patterns and their colours. The definitive source for these records. It is a United States standard; other national surveys use related but not identical patterns, and records say so rather than presenting one national convention as universal.
British Geological Survey mapping and legend conventions
British Geological Survey · retrieved 2026-08-24
Cited where British practice differs from the United States standard, chiefly in lithologic ornament. Used for identity and current use, not for the interpretation of any particular mapped area.

Last reviewed 2026-08-24

Meanings

On a geological map a basalt is ornamented with fine angular marks, the standard pattern for a fine-grained extrusive igneous rock.

Officially standardisedVerified fact

Marks a basalt or similar fine-grained extrusive igneous rock.

Contexts: Maps

Officially standardisedVerified fact

Uses a finer ornament than granite, the density of the pattern following the grain size of the rock it stands for.

Contexts: Maps

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Geologic map
Wikipedia · retrieved 2026-08-24
Tertiary reference. Used for how a structural symbol is read and for the plain-language name of a feature. Structural definitions follow the cartographic standard.
FGDC Digital Cartographic Standard for Geologic Map Symbolization
United States Geological Survey for the Federal Geographic Data Committee · retrieved 2026-08-24
An openly published national standard defining geologic map symbols, lithologic patterns and their colours. The definitive source for these records. It is a United States standard; other national surveys use related but not identical patterns, and records say so rather than presenting one national convention as universal.
British Geological Survey mapping and legend conventions
British Geological Survey · retrieved 2026-08-24
Cited where British practice differs from the United States standard, chiefly in lithologic ornament. Used for identity and current use, not for the interpretation of any particular mapped area.

Last reviewed 2026-08-24