Porphyry

Dacite

Porphyry and Dacite

Porphyry

Dacite

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Definition

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

Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite

History

Origin

Egypt

Romania and Moldova, Europe

Discoverer

Unknown

Etymology

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

From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described

Class

Igneous Rocks

Sub-Class

Durable Rock, Hard Rock

Durable Rock, Soft Rock

Family

Group

Plutonic

Volcanic

Other Categories

Fine Grained Rock, Opaque Rock

Fine Grained Rock, Medium Grained Rock, Opaque Rock

Texture

Porphyritic

Aphanitic to Porphyritic

Color

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

Bluish - Grey, Brown, Grey, Light to Dark Grey

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Vesicular

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Decorative Aggregates, Entryways, Interior Decoration

Exterior Uses

Garden Decoration, Paving Stone

As Building Stone, Paving Stone, Garden Decoration

Other Architectural Uses

Curbing

Industry

Construction Industry

Construction Aggregate

As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping

Medical Industry

Antiquity Uses

Artifacts, Monuments, Sculpture

Artifacts

Other Uses

Commercial Uses

Creating Artwork, Gemstone, Jewelry

Commemorative Tablets, Creating Artwork

Types

Rhomb Porphyry

Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite

Features

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

Host Rock for Lead, Is one of the oldest rock

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Formation

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.

Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Further, the Oceanic crust is hydrothermally altered as quartz and sodium are added.

Composition

Mineral Content

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

Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon

Compound Content

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

Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

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

Burial Metamorphism, Cataclastic Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Chemical Erosion

Properties

Physical Properties

Hardness

6-72-2.25

1 7

👆🏻

Grain Size

Fine Grained

Medium to Fine Coarse Grained

Fracture

Irregular

Conchoidal

Streak

White

Porosity

Less Porous

Luster

Dull

Subvitreous to Dull

Compressive Strength

150.00 N/mm²70.00 N/mm²

0.15 450

👆🏻

Cleavage

Perfect

Toughness

1.7

Specific Gravity

2.5-42.86-2.87

0 8.4

👆🏻

Transparency

Translucent to Opaque

Translucent

Density

2.5-2.52 g/cm³2.77-2.771 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.71 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant

Reserves

Deposits in Eastern Continents

Asia

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

Africa

Egypt, Ethiopia, Ghana, South Africa

Europe

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

France, Greece, Romania, Scotland, Spain

Others

Greenland

Deposits in Western Continents

North America

Canada, Cuba, Jamaica, USA

USA

South America

Bolivia, Brazil, Colombia, Ecuador, Paraguay

Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Western Australia

New Zealand, South Australia, Western Australia

All about Porphyry and Dacite Properties

Know all about Porphyry and Dacite properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry and Dacite belong to Igneous Rocks.Texture of Porphyry is Porphyritic whereas that of Dacite is Aphanitic to Porphyritic. Porphyry appears Dull and Dacite appears Vesicular. The luster of Porphyry is dull while that of Dacite is subvitreous to dull. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas Dacite is available in bluish - grey, brown, grey, light to dark grey colors. The commercial uses of Porphyry are creating artwork, gemstone, jewelry and that of Dacite are commemorative tablets, creating artwork.