Metamorphic Rocks Gallery
Select or click a metamorphic rock name to view photos and some facts about the rock.
Anthracite
Sample shows the compact nature of anthracite, no grains distinguishable with the naked eye. Anthracite will fracture leaving uneven broken surfaces and has a submetallic luster giving it a shiny appearance.
Texture: Non-foliated
Grain Size: Fine
Metamorphic grade: Low
Mineralogy: Carbon
Protolith: Bituminous coal
Metamorphic Environment: Regional
Interesting Facts: Unlike other ranks of coal which are sedimentary, anthracite is metamorphic and is the highest rank of coal. Anthracite produces the greatest heat and burns the cleanest of all the types of coal. It produces no smoke when burned!
Cataclasite
Sample shows the cohesive nature of cataclasite with large angular to sub angular grains in a fine matrix.
Texture: Non-foliated
Grain Size: Coarse
Metamorphic Grade: Low to intermediate
Mineralogy: Varied
Protolith: Varied
Metamorphic Environment: Dynamic
Interesting Facts: This rock is formed in fault zones in the upper crust. Rocks trapped in this fault zone experience high levels of shear stress.
Granite Gneiss
This sample shows the alternating light and dark colored bands, defined by the preferred arrangement of the minerals, characteristic of the Gneissic texture of this high grade metamorphic rock.
Texture: Foliated
Grain Size: Coarse
Metamorphic Grade: High
Mineralogy: Predominantly quartz, pink and white feldspar. Biotite, muscovite, amphibole or pyroxene may be present
Protolith: Granite
Metamorphic Environment: Regional
Interesting Facts: Granite gneiss is commonly used for building stone, decorative wall covering, counter tops, statues and gravestones.
Garnet Muscovite Schist
Sample shows well developed schistosity, characterized by the layered muscovite micas. The prominent euhedral garnet porphyroblasts, approximately 1/4 inch in diameter, are distinctive.
Texture: Foliated
Grain Size: Medium
Metamorphic Grade: Intermediate
Mineralogy: Dominant minerals are garnet and muscovite. Biotite, quartz and feldspar may also be present.
Protolith: Shale, mudstone or felsic igneous rocks
Metamorphic Environment: Regional
Interesting Facts: Garnet muscovite schists have been used for building stone, decorative wall covering and jewelry.
Marble
Sample illustrates the non- foliated (granoblastic) texture of Marble. The coarse crystal size infers that the sample was formed under intermediate grade metamorphic conditions, of medium temperatures and pressures in a contact metamorphic environment.
Texture: Non- foliated
Grain Size: Coarse to fine
Metamorphic Grade: Variable (low to high)
Mineralogy: Calcite
Protolith: Limestone
Metamorphic Environment: Contact or regional
Interesting Facts: Marble is commonly used for buildings, statues, decorative stone and tile. The taj mahal in India, one of the seven wonders of the world, is built from white marble blocks. Marble will effervesce in a weak hydrochloric acid solution!
Phyllite
Sample shows the wavy foliated arrangement of the micas and the characteristic phyllite “sheen” as a result of the vitreous luster of the micas present. This easily distinguishes this rock sample from slate.
Texture: Foliated
Grain Size: Medium
Metamorphic Grade: Low
Mineralogy: Predominantly micas and chlorite. Quartz and feldspar may be present
Protolith: Shale or mudstone
Metamorphic Environment: Regional
Interesting Facts: Phyllite is commonly used for floor tiles, decorative stone and building facades.
Quartzite
Sample shows the coarse grained, non foliated equigranular texture of quartzite. The color of the sample indicates that the protolith was a quartz sandstone with little to no accessory minerals.
Texture: Non- foliated
Grain Size: Coarse to fine
Metamorphic Grade: Variable (low to high)
Mineralogy: Quartz
Protolith: Quartz rich sandstone
Metamorphic Environment: Contact or regional
Interesting Facts: Quartzite is commonly used for flooring tiles, countertops, decorative stone and statues.
Red Quartzite
Sample shows coarse grained non foliated equigranular texture of quartzite. The red color of this sample is a result of iron content, hematite is the most likely source.
Texture: Non- foliated
Grain Size: Coarse to fine
Metamorphic Grade: Variable (low to high)
Mineralogy: Quartz
Protolith: Quartz rich sandstone
Metamorphic Environment: Contact or regional
Interesting Facts: Red quartzite is commonly used for flooring tiles, countertops, decorative stone and statues.
Schist
Sample shows well developed schistosity, characterized by the layering of the abundant mica minerals. The coarse grained nature of the sample distinguishes it from a phyllite.
Texture: Foliated
Grain Size: Medium
Metamorphic Grade: Intermediate
Mineralogy: Dominant mineral is muscovite. Biotite, quartz, and feldspar may also be present.
Protolith: Shale or mudstone
Metamorphic Environment: Regional
Interesting Facts: The “glittery” appearance of schist make them useful for decorative landscaping rocks as well as building facades.
Slate, Black
Sample shows foliation characterized by the distinctive rock cleavage (easily splits along the layers of this rock). Slate is denser than its parent rock and very fine grained. The black color of this sample is due to high carbon content and presence of minerals like graphite.
Texture: Foliated
Grain Size: Fine grained
Metamorphic Grade: Low
Mineralogy: Clay minerals, quartz, mica, and feldspar
Protolith: Mudstone, shale
Metamorphic Environment: Regional
Interesting Facts: Slate is a good electrical insulator and was used to case early fuse boxes. Today slate is commonly used for flooring, wall tile, roof tiles, and table tops.
Slate, Gray
Sample shows foliation characterized by the distinctive rock cleavage (easily splits along the layers of this rock) and porphyroblasts (possibly quartz). Slate is denser than its parent rock and very fine grained.
Texture: Foliated
Grain Size: Fine grained
Metamorphic Grade: Low
Mineralogy: Clay minerals, quartz, mica, and feldspar
Protolith: Mudstone, shale
Metamorphic Environment: Regional
Interesting Facts: Slate is a good electrical insulator and was used to case early fuse boxes. Today slate is commonly used for flooring, wall tile, roof tiles, and table tops
Slate, Red
Sample shows foliation characterizes by the distinctive rock cleavage present Fine grained texture High iron oxide content results in the red color of this variety of slate.
Texture: Foliated
Grain Size: Fine grained
Metamorphic Grade: Low
Mineralogy: Clay minerals, quartz, mica, and feldspar
Protolith: Mudstone, shale
Metamorphic Environment: Regional
Interesting Facts: Slate is a good electrical insulator and was used to case early fuse boxes. Today slate is commonly used for flooring, wall tile, roof tiles, and table tops.
References
- Geologyscience.com (2021). Slate. [online] Available at: https://geologyscience.com/rocks/metamorphic-rocks/slate/ [6th July 2021 ]
- Pellant, C. (1992). Rocks and minerals. 1st American ed. New York: Dorling Kindersley.