Chert

Porphyry

Chert and Porphyry

Chert

Porphyry

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Definition

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

Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix

History

Origin

Egypt

Discoverer

Unknown

Etymology

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

From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites

Class

Sedimentary Rocks

Igneous Rocks

Sub-Class

Durable Rock, Hard Rock

Family

Group

Plutonic

Other Categories

Fine Grained Rock, Opaque Rock

Texture

Banded, Rough

Porphyritic

Color

Black, Brown, Green, Grey, Red, White

Black, Brown, Green, Grey, Red, Rust, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Glassy or Pearly

Dull

Uses

Architecture

Interior Uses

Decorative Aggregates, Homes

Decorative Aggregates, Interior Decoration

Exterior Uses

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

Garden Decoration, Paving Stone

Other Architectural Uses

Curbing

Industry

Construction Industry

Arrowheads, Construction Aggregate, Cutting Tool, Spear Points

Construction Aggregate

Medical Industry

Antiquity Uses

Artifacts, Monuments

Artifacts, Monuments, Sculpture

Other Uses

Commercial Uses

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

Creating Artwork, Gemstone, Jewelry

Types

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

Rhomb Porphyry

Features

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

Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Present

Absent

Formation

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.

Porphyry is formed in two stages: the magma cools slowly deep within the crust or the magma is cools rapidly as it erupts from a volcano, creating small grains that are usually invisible to naked eye.

Composition

Mineral Content

Quartz, Silicon

Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica

Compound Content

Silicon Dioxide

Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Properties

Physical Properties

Hardness

6.5-76-7

1 7

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Grain Size

Very fine-grained

Fine Grained

Fracture

Uneven, Splintery or Conchoidal

Irregular

Streak

White

Porosity

Highly Porous

Less Porous

Luster

Waxy and Dull

Dull

Compressive Strength

450.00 N/mm²150.00 N/mm²

0.15 450

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Cleavage

Toughness

1.5

1.7

Specific Gravity

2.5-2.82.5-4

0 8.4

👆🏻

Transparency

Translucent to Opaque

Density

2.7 g/cm³2.5-2.52 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.74 kJ/Kg K0.71 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant

Heat Resistant, Impact Resistant

Reserves

Deposits in Eastern Continents

Asia

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

China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam

Africa

Kenya, Morocco, South Africa, Tanzania

Egypt, Ethiopia, Ghana, South Africa

Europe

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

Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland

Others

Greenland, Mid-Atlantic Ridge

Greenland

Deposits in Western Continents

North America

Canada, Mexico, USA

Canada, Cuba, Jamaica, USA

South America

Bolivia, Brazil

Bolivia, Brazil, Colombia, Ecuador, Paraguay

Deposits in Oceania Continent

Australia

New South Wales, Queensland, South Australia, Western Australia

New South Wales, New Zealand, Western Australia

All about Chert and Porphyry Properties

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