Hornfels

Chert

Hornfels and Chert

Hornfels

Chert

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Definition

Hornfels is a metamorphic rock formed by the contact between mudstone or other clay rich rock, and a hot igneous body, and represents a heat altered equivalent of the original rock

Chert is a hard, dark, opaque sedimentary rock which is composed of silica with an amorphous fine-grained texture

History

Origin

New Zealand

Discoverer

Unknown

Etymology

From German which means hornstone

From flint-like quartz, 1670s, of unknown origin- a local term, which has been taken into geological use

Class

Metamorphic Rocks

Sedimentary Rocks

Sub-Class

Durable Rock, Soft Rock

Durable Rock, Hard Rock

Family

Group

Other Categories

Fine Grained Rock, Opaque Rock

Texture

Granular, Platy

Banded, Rough

Color

Brown, Dark Greenish - Grey, Green, Reddish Brown

Black, Brown, Green, Grey, Red, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Glassy or Pearly

Uses

Architecture

Interior Uses

Decorative Aggregates, Flooring, Homes, Interior Decoration

Decorative Aggregates, Homes

Exterior Uses

As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone

As Building Stone, As Facing Stone, Garden Decoration, Office Buildings

Other Architectural Uses

Curbing

Industry

Construction Industry

for Road Aggregate, Roadstone

Arrowheads, Construction Aggregate, Cutting Tool, Spear Points

Medical Industry

Antiquity Uses

Artifacts, Monuments

Other Uses

Commercial Uses

Cemetery Markers, Commemorative Tablets, Creating Artwork

Creating Artwork, Gemstone, In fire-starting tools, Jewelry, To ignite fire, Used in flintlock firearms

Types

Biotite hornfels

Flint, Jasper, Radiolarite, Common Chert, Chalcedony, Agate, Onyx, Opal, Magadi-type Chert, Porcelanite, Siliceous Sinter

Features

Smooth to touch

Clasts are smooth to touch, Easily splits into thin plates, Has High structural resistance against erosion and climate

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Present

Formation

Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Hornfels is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.

Chert forms when microcrystals of silicon dioxide grow within soft sediments that become limestone or chalk. The chert formation can be either of chemical or biological origin.

Composition

Mineral Content

Andalusite

Quartz, Silicon

Compound Content

Fe, Mg

Silicon Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion

Chemical Erosion

Properties

Physical Properties

Hardness

2-36.5-7

1 7

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Grain Size

Fine Grained

Very fine-grained

Fracture

Conchoidal

Uneven, Splintery or Conchoidal

Streak

White

Porosity

Highly Porous

Luster

Shiny

Waxy and Dull

Compressive Strength

5.80 N/mm²450.00 N/mm²

0.15 450

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Cleavage

Perfect

Toughness

1.5

Specific Gravity

3.4-3.92.5-2.8

0 8.4

👆🏻

Transparency

Opaque

Translucent to Opaque

Density

0.25-0.30 g/cm³2.7 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.84 kJ/Kg K0.74 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant, Pressure Resistant

Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant

Reserves

Deposits in Eastern Continents

Asia

Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand

China, India, Iran, Japan, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam

Africa

Cameroon, East Africa, Tanzania, Western Africa

Kenya, Morocco, South Africa, Tanzania

Europe

United Kingdom

Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom

Others

Greenland, Mid-Atlantic Ridge

Deposits in Western Continents

North America

Canada, USA

Canada, Mexico, USA

South America

Bolivia, Brazil, Colombia, Ecuador

Bolivia, Brazil

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Queensland, Western Australia

New South Wales, Queensland, South Australia, Western Australia

All about Hornfels and Chert Properties

Know all about Hornfels and Chert properties here. All properties of rocks are important as they define the type of rock and its application. Hornfels belongs to Metamorphic Rocks while Chert belongs to Sedimentary Rocks.Texture of Hornfels is Granular, Platy whereas that of Chert is Banded, Rough. Hornfels appears Dull and Chert appears Glassy or Pearly. The luster of Hornfels is shiny while that of Chert is waxy and dull. Hornfels is available in brown, dark greenish - grey, green, reddish brown colors whereas Chert is available in black, brown, green, grey, red, white colors. The commercial uses of Hornfels are cemetery markers, commemorative tablets, creating artwork and that of Chert are creating artwork, gemstone, in fire-starting tools, jewelry, to ignite fire, used in flintlock firearms.