Abbreviation
|
Texture/structure
|
Definition
|
|---|---|---|
| Phenocryst percent: | ||
| a | Aphyric | <1% |
| sp | Sparsely phyric | 1%-2% |
| mp | Moderately phyric | 2%-10% |
| hp | Highly phyric | >10% |
| Groundmass crystallinity: | ||
| c | Holocrystalline | 90%-100% crystals |
| hc | Hypocrystalline | 50%-90% crystals |
| hyh | Hypohyaline | 10%-50% crystals |
| G | Hyaline | 0%-10% crystals |
| Grain size: | ||
| pc | Phanerocrystalline | Phaneritic |
| cg | Coarse grained | >5 mm |
| mg | Medium grained | 2-5 mm |
| fg | Fine grained | 1-2 mm |
| ap | Aphanitic | <1 mm |
| mc | Microcrystalline | <0.5 mm (= aphanitic) |
| cc | Cryptocrystalline | Not visible under binocular microscope (= aphanitic) |
| Vesicularity: | ||
| nov | Nonvesicular | <1% |
| spv | Sparsely vesicular | 1%-5% |
| mov | Moderately vesicular | 5%-20% |
| hiv | Highly vesicular | >20% |
| Alteration log: | ||
| v | Veins | |
| f | Unaltered | <2% |
| s | Slight | 2%-10% |
| m | Moderate | 10%-40% |
| h | High | 60%-80% |
| vh | Very high | 80%-95% |
| co | Complete | 95%-100% |
| Mineral form: | ||
| e | Equant | |
| t | Tabular | |
| b | Bladelike or lathlike | |
| Vesicle type and vesiculation structure: | ||
| ve | Vesicles | |
| vd | Diktytaxitic texture | |
| pv | Pipe vesicles | Hollow |
| sv | Segregation vesicles | |
| vc | Vesicle cylinder | Filled with vesicular segregation material |
| hvs | Horizontal vesicle sheets | Segregation veins; filled with vesicular segregation material |
| mv | Megavesicles | Domed roof and flat floors, may have segregation material at their base |
| vz | Vesicular zone | >10 vol% macroscopic vesicles |