Rock

There are three kinds of rock: igneous, sedimentary, and metamorphic.
Igneous rocks form when molten rock (magma or lava) cools and solidifies.
Sedimentary rocks originate when particles settle out of water or air, or by precipitation of minerals from water. They accumulate in layers.
Metamorphic rocks result when existing rocks are changed by heat, pressure, or reactive fluids, such as hot, mineral-laden water. Most rocks are made of minerals containing silicon and oxygen, the most abundant elements in the earth’s crust.
There are a variety of Hardstone rocks we see in Dierde used for a variety of purposes. Rocks are important for those who look for precious metals and gems.

Igneous Rocks

Igneous rocks solidify from molten rock (called magma within the Earth and lava on the surface). They are identified by mineral content and texture — the size and shape of their mineral grains.
Texture is controlled by the rate of cooling: magma that cools slowly deep in the Earth forms rock with large crystals, and lava that cools quickly on the surface forms fine-grained rock.

Granite Pegmatite

This rock formed deep in the crust, near the top of a crystallizing magma chamber. It is composed of the minerals quartz (gray), orthoclase (pink), albite (white), and mica (dark and platy). The larger crystals grew more slowly than the smaller crystals.

Diabase

This rock solidified from a basaltic magma within a few hundred meters of the surface, probably beneath a volcano. It cooled rapidly, giving it a fine-grained, peppery appearance. The black mineral is pyroxene, and the white one is plagioclase.

Diorite

This rock crystallized in a mountain belt. It contains the minerals plagioclase (white) and hornblende (black).
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Sedimentary Rocks

Sedimentary rocks are layered. Some form when particles of rocks and minerals settle out of water or air. Others form when minerals precipitate directly out of water. Sedimentary rocks are identified by their minerals and texture.
As the sediments pile up, water is driven out by the weight of the overlying pile, and minerals precipitate around the sediment particles, cementing them into rock. This process is called lithification.

Limestone

Limestone is one of the most widespread sedimentary rocks. Many organisms, from corals to microscopic foraminifera, grow shells composed of carbonates. Most limestone forms when these organisms die and their carbonate shells accumulate in shallow seas.

Shale

Shale is made up clay and silt, particles that are finer than sand. Clay and silt are deposited in slow-moving rivers, at the far ends of deltas, and in other quiet environments where slow-moving water cannot keep the particles suspended.

Sandstone

Sandstone is made of sand, which accumulates in rivers and along ocean shores where water moves fast enough to remove the finer particles. Sandstones can also be deposited by winds to form sand dunes.
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Metamorphic Rocks

Metamorphic rocks form when sedimentary, igneous, or pre-existing metamorphic rocks are changed by heat, pressure, and chemically reactive waters. These rocks are identified by their minerals and texture.
During metamorphism, new minerals grow, with different sizes, shapes, and orientations than those of the original minerals. The chemical composition of the original rock may also change, as some elements are carried away and others are added by the fluids flowing through the rocks.

Manhattan Schist

Originally a shale, this schist now consists of dark, biotite-rich layers and finer-grained, light-colored layers made of gray quartz and white orthoclase. The distinct layering developed perpendicular to the direction of compression. This schist underlies most of Manhattan.

Slate

This slate was also once a shale. Because the shale was metamorphosed only slightly, its textures changed little. This sample is from the Grenville slate, widely used for roofing.

Gneiss

This rock was once a granite. As it was deformed by heat and pressure, the original even-grained rock developed dark layers, primarily biotite, and light layers, mostly gray quartz, pink orthoclase, and black hornblende.
Source
See Also: https://www.gemsociety.org/article/gem-formation/
https://www.gemrockauctions.com/learn/technical-information-on-gemstones/how-do-gemstones-form
https://www.diamond-heaven.co.uk/dh/blog/article/what-s-the-difference-between-diamonds-and-other-gemstones/133

Type

Ore/Mineral