Rocks projects

Metamorphic Rock

Description: Metamorphic rocks have been modified by heat, pressure, and chemical process usually while buried deep below Earths surface. If metamorphic rocks do not get enough heat to melt they turn in to igneous rocks. In metamorphic rocks some or all of the minerals in the original rock are replaced, atom by atom, to form new minerals.


Definition:  Slate is a low grade metamorphic rock generally formed by the metamorphic of mudstone/shale, or sometimes basalt.

Slate texture: Foliated

Color: Black, blue, green, red, brown

Features: Smooth to touch

Hardness: Hard and brittle


Definition: Quartzite is a metamorphic rock formed when quartz-rich sandstone or chert has been exposed to high temperatures and pressures. Quartzite is not able to be scratch by a metal blade.

Quartzite texture: Granular

Color: Has a wide variety of colors

Features: Gritty to touch

Hardness: Hard


Gneiss is a high grade metamorphic rock, meaning that it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of granite, or sedimentary rock. Gneiss displays distinct foliation representing alternating layers composed of different minerals.

Gneiss texture: Foliated

Color: Light and dark colors

Hardness: Hard

Features: rough to touch

Definition: Schist is a medium metamorphic rock, formed by the metamorphosis of mudstone/ shale, or some types of igneous rock, to a higher degree than slate. It has been subjected to higher temperatures and pressure.

Schist texture: Foliated

Color: Lighter and darker bands, often shiny

Features: Smooth but not smooth touch

Hardness: Generally hard


Description: Marble is a metamorphic rock formed when limestone is exposed to high temperatures and pressure. Marble forms under such conditions. Because the calcite forming limestone. Under increase temperature and/ or pressure existing minerals become unstable and break down to form new minerals.

Marble texture: Granular

Color: Wide variety of colors

Hardness: Hard, although component mineral is soft

Features: Gritty to touch

Igneous rocks

Igneous rock is formed through cooling and solidification of magma or lava. In Latin ignis means fire. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of earths crust.


Description: Gabbro is a dense intrusive rock. It is often found along mid-ocean ridges or in ancient mountains composed and compressed and up lifted oceanic crust.

Gabbro texture: Phaneritic

Color: Dark grey to black


Description: Granite is a felsic it's a light colored rock. It comprises some of the oldest known rocks on earth. Granite lies in the corners of all the continents. Granite is the plutonic equivalent of rhyolite.

Granite texture: Phaneritic

Color: typically light-colors


Definition: Basalt a mafic extrusive rock, is the most widespread of igneous rocks. Because of low content basalt lava has a low viscosity, and forms thin flows that can travel long distances. It is also found as intrusive dikes and sills.

Basalt texture: Aphanitic

Color: Dark grey to black


Definition: Diorite is an intrusive rock intermediate composition between Gabbro and granite. It is produced in volcanic arcs, and in mountain building where it can occur in large volumes as batholiths roots of mountains.

Diorite texture: Phaneritic

Color: Typically speckled black and white


Definition: Peridotite is a very dense, coarse- grained, olivine- rich, ultra- mafic intrusive rock. Peridotite has a low silica content, and contains very little or no feldspar. It is a common componentof oceanic lithosphere, and is derived from the upper mental. It is found on land as part of oceanic crust sequences called ophiolites.

Peridotite texture: Phaneritic

Color: Generally dark greenish- grey

Sedimentary rock

Definition: Sedimentary rocks are the product of the erosion of existing rocks. Eroded material accumulates as sediment, either in the sea or on land, and is then buried, compacted and cemented to produce sedimentary rock.


Definition: There are mant different types of limestone formed through a variety of processes. Limestone can be precipitated from water. Limestone is made of different things for example shells of Dead Sea creatures. Limestone is a sedimentary rock consisting of more than 50% calcium carbonate.

Limestone texture: Clastic or non- clastic

Hardness: Generally hard

Color: Variable, But generally light colored, grey through yellow.


Definition: Sandstone is a sedimentary rock formed from cemented sand-sized calcite, silica or iron oxides.

Sandstone texture: Clastic

Hardness: Soft and hard

Color: through grey, yellow, red to white reflecting the variation in mineral content and cement.

Features: Gritty to touchd


Definition: Chert is a sedimentary rock consisting almost entirely of silica (SiO2), and can form in a variety of ways. Replacement chert forms when other material is replaced by silica, e.g. petrified wood forms when silica rich fluids percolate through dead wood and the silica precipitates to replace the wood. Chert can also form through direct precipitation from silica rich fluids.

Chert texture: Non-clastic

Hardness: hard

Color: all colors, dependent on impurities present when precipitated.


Definition: Argillite is highly indurated mudstone. Along with greywacke, it comprises the basement rock of New Zealand, and so is an important rock type throughout the country. Because it has been subjected to significant amounts of tectonic movement over a long period of time (some New Zealand argillite is over 300 million years old).

Argillite texture: clastic

Hardness: hard

Color: grey to black, also green and red


Definition; Greywacke is variety of argillaceous sandstone that is highly indurated and poorly sorted. It comprises a large percentage of the basement rock of New Zealand, and so is an important rock type throughout the country. Because it has been subjected to significant amounts of tectonic movement over a long period of time.

Greywacke texture: Clastic

Hardness: hard

Color: grey to black; often with white quartz veins