Hornfels vs. Hornblende — What's the Difference?

A dense, non-foliated metamorphic rock.

Commonly found in igneous and metamorphic rocks.

Lacks any original texture from the parent rock.

Often associated with high pressure and temperature conditions.

Composition varies based on the protolith.

Forms elongated and prismatic crystals.

Rock formed by the heat from nearby magma.

A dark, green to black amphibole mineral.

Usually fine-grained and tough.

Contains silicate of iron and magnesium.

Hornfels is the group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. These properties are due to fine grained non-aligned crystals with platy or prismatic habits, characteristic of metamorphism at high temperature but without accompanying deformation.

Hornblende is a complex inosilicate series of minerals (ferrohornblende – magnesiohornblende). It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole.

A fine-grained metamorphic rock composed of quartz, feldspar, mica, and other minerals, formed by the metamorphism of sedimentary rocks from heat associated with magma.

The most common mineral in the amphibole group, CaNa(Mg,Fe)4(Al,Fe,Ti)3Si6O22(OH,F)2 commonly green to black, found in igneous and metamorphic rocks.

Any of a series of contact metamorphic rocks that have been baked and indurated by the heat of intrusive igneous masses and rendered massive, hard, splintery, and in some cases exceedingly tough and durable.

(mineral) A green to black amphibole mineral, of complex structure, formed in the late stages of cooling in igneous rock.

A fine-grained metamorphic rock formed by the action of heat on clay rocks

The common black, or dark green or brown, variety of amphibole. (See Amphibole.) It belongs to the aluminous division of the species, and is also characterized by its containing considerable iron. Also used as a general term to include the whole species.

A green to black mineral of the amphibole group; consists of silicates of calcium and sodium and magnesium and iron

Hornfels is formed through contact metamorphism, where rocks are heated by nearby magma but not significantly deformed.

Hornfels is primarily used as a construction aggregate and in decorative stonework.

Hornblende is most commonly found in both igneous and metamorphic rocks, such as granites and amphibolites.

Yes, hornfels can contain a variety of minerals including hornblende, depending on its protolith.

Hornblende is identified by its dark color, prismatic crystals, and composition of calcium, magnesium, iron, and aluminum silicates.

Hornfels is formed from the heat of magma without deformation, while hornblende forms under both high pressure and temperature as part of a rock's mineral content.

Hornfels can vary widely in color, but it is typically grey or black, depending on its mineral content.

Hornblende is significant in geological studies for identifying high-pressure and high-temperature conditions during rock formation.

The texture of hornfels is fine-grained and massive, with a lack of foliation.

Hornblende's chemical formula can vary but generally includes (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH)2.

While hornfels is generally not used in jewelry due to its lack of translucence and typical color, its toughness can be appreciated in other decorative applications.

Yes, hornfels is considered very hard and durable, which makes it suitable for construction and decorative purposes.

Yes, the presence of hornblende can significantly influence the classification and properties of the rock it inhabits.

The mineral composition of hornfels varies based on the original rock or protolith, which can include minerals like quartz, feldspar, and biotite.

Hornblende helps in identifying rock types and their conditions of formation due to its specific mineral makeup and crystal habits.