What is a hornfels rock?
What is a hornfels rock?
Hornfels is medium-to-coarse crystalline metamorphic rocks formed out of contact metamorphism, dark color, and rich in silicates with granoblastic and porphyroblastic texture.
What are the characteristics hornfels rock?
Key properties of the rock include velvety texture and appearance, conchoidal fracture, and fine grain. It may be very hard and tough. It is a contact metamorphic rock, formed when magma bakes its source material.
What is a hornfels how is it formed?
All of the rocks called hornfels—a hard, fine-grained, flinty rock—are created when heat and fluids from the igneous intrusion alter the surrounding rock, changing its original mineralogy to one that is stable under high temperatures.
What type of metamorphism rock is hornfels?
|Color||mottled brownish green|
Where is hornfels formed?
Hornfels most commonly form in the aureole of granitic intrusions in the upper or middle crust. Hornfels formed from contact metamorphism by volcanic activity very close to the surface can produce unusual and distinctive minerals.
Is hornfels a rock or a mineral?
Hornfels is a metamorphic rock formed by the contact between mudstone / shale, or other clay-rich rock, and a hot igneous body, and represents a heat-altered equivalent of the original rock.
How do you identify hornfels?
Under a microscope the structure of hornfels is very distinctive, with small, generally equigranular, mineral grains fitting closely together like the fragments of a mosaic or a rough pavement. Texture – granular, platy or elongate crystals randomly oriented so no foliation evident.
Is hornfels foliated?
Hornfels is another non-foliated metamorphic rock that normally forms during contact metamorphism of fine-grained rocks like mudstone or volcanic rock (Figure 7.13). In some cases, hornfels has visible crystals of minerals like biotite or andalusite.
Is hornfels a sedimentary rock?
Hornfels is a type of metamorphic rock that gets its name from its resemblance to animal horn. Hornfels forms when magma heats other rock, which may be igneous, metamorphic, or sedimentary. The most common colors of hornfels are black and dark brown. It may be banded or occur in other colors.
Does hornfels have layers?
In contrast to schists and gneisses, hornfelses show little or no foliation or layering. They form under conditions of approximately anisotropic (directionless) stress, so there is no tendency for the crystals to align in any particular direction.
Is hornfels foliated or non foliated?
What is the luster of hornfels?
The most common hornfels (the biotite hornfels) are dark-brown to black with a somewhat velvety luster owing to the abundance of small crystals of shining black mica.
What is hornfels used for?
The primary use of hornfels is in architecture. The hard, interesting-looking stone may be used to make interior flooring and decorations as well as exterior facing, paving, curbing, and decorations. The rock is used in the construction industry to make road aggregate.
Where is hornfels commonly found?