Geology

Felsic Flow

Volcanic extrusive. Light /white weathering rock with no distinguishing crystals except possible quartz.

Intermediate Flow

Volcanic extrusive. Pale grey-green rock, very fine-grained, no evident minerals.

Intermediate Pyroclastic

Volcanic extrusive, with different types of pale grey-green angular clasts.

Mafic Massive Flow

Volcanic extrusive, dark to medium green, homogeneous, fine-grained, no visible crystals, may have relict gas bubbles filled with quartz or calcite.

Mafic Pillowed Flow

Volcanic extrusive, green with round structures defined by quenched rinds (selvages), commonly with lighter or darker alteration.

Gabbro

Plutonic intrusive, dark green or black with 35-90% dark mafic minerals visible (>3mm).

Tonalite

Plutonic intrusive. Grey, fine- to medium grained commonly with 15% biotite visible.

Granodiorite

Plutonic intrusive.

Granite

Plutonic intrusive. Pink or white with >20% quartz and pink and white feldspars.

Kimberlite

Plutonic. Dark, silica-poor, magnesium-rich igneous rock with highly variable mixture of melt, minerals crystallizing from the melt, foreign crystals and rock pieces, which may contain diamonds (H=10) carried rapidly from depths of 150-450 km.

Dykes and Sills

Plutonic intrusive, crystallized magma that cuts across rock units vertically (dykes) or horizontally (sills).

Porphyry

Rocks with crystals much larger than groundmass (i.e., spotted). Indicates 2-stage cooling, slow (growing phenocrysts) then fast (fine groundmass) reflecting initial intrusive (slow crystallization) setting evolved to extrusive (fast cooling) setting.