Metamorphic rocks can be classified into one of three sub-families:

Unfoliated -

Foliated -

Deformed -

A banded rock splitting more or less evenly into layers, usually results from the combination of both heat and pressure (gneiss).

A rock with no definite layers or bands, splits randomly, primarily due to heat effects (marble).

Parent rock is stretched and deformed but relatively identifiable (metaconglomerate - stretched pebble).

MetamorphicGrade

Low

Grade

Medium

Grade

High

Grade

Slate

Schist

Gneiss

Conditions not found in nature

Phyllite

Look at your own metamorphic rocks while viewing the

following slides.

You should have a sense of metamorphic rocks before

completing the identification activity

Foliated Rocks - Slate and Phyllite

Black slate Red slate

Phyllite - light Phyllite - dark

Foliated Rocks - Schist and Gneiss

Gneiss

Schist Mica Schist

Gneiss close up showing mineral layers

1 cm

Unfoliated Rocks - Marble

Right - Pure white marble; Northern Italy.

Below - Banded marbles; the bands are from the original deposits and/or different minerals.

Unfoliated Rocks - Quartzite

Quartzite is hard and breaks across the grains whereas

sandstone breaks between the grains.

Why does this difference exist?

What does our sample of quartzite look like?

Deformed Rocks - Stretched Pebble Conglomerate(metaconglomerate)

The pale coloured quartzite pebbles have been visibly stretched but are still quite identifiable.

The Rock Cycle

West Coast Rocking - The Rock Cycle in Action

C & T p. 21

The EndThe End