Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Tachylite is a vitreous form of basaltic volcanic glass. This glass is formed naturally by the rapid cooling of molten basalt
Discoverer
Unknown
Unknown
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From German Tachylite, from tachy- + Greek lutos soluble, melting
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Other Categories
Fine Grained Rock, Opaque Rock
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Porphyritic
Vitreous
Color
Black, Brown, Green, Grey, Red, Rust, White
Black, Dark Brown
Durability
Durable
Durable
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
Construction Aggregate
Cutting Tool, Knives, Landscaping, Scrapers
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts
Commercial Uses
Creating Artwork, Gemstone, Jewelry
Cemetery Markers, Creating Artwork
Types
Rhomb Porphyry
Volcanic glass
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Available in Lots of Colors and Patterns, Clasts are smooth to touch
Archaeological Significance
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.
Tachylite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Feldspar, Olivine
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Fe, Mg
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Sea Erosion, Water Erosion, Wind Erosion
Grain Size
Fine Grained
Medium to Fine Coarse Grained
Fracture
Irregular
Conchoidal
Porosity
Less Porous
Less Porous
Specific Gravity
2.5-4
2.4
Transparency
Translucent to Opaque
Opaque
Density
2.5-2.52 g/cm3
3.058 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
Cambodia, Russia, South Korea
Africa
Egypt, Ethiopia, Ghana, South Africa
East Africa
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
England, Germany, Hungary, Iceland, Scotland, Sweden
Others
Greenland
Hawaii Islands
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
USA
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
-
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
Victoria
Porphyry vs Tachylite Characteristics
Though some rocks look identical, they have certain characteristics which distinguish them from others. Characteristics of rocks include texture, appearance, color, fracture, streak, hardness etc. Porphyry vs Tachylite characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Porphyry and Properties of Tachylite. Learn more about Porphyry vs Tachylite in the next section. The interior uses of Porphyry include Decorative aggregates and Interior decoration whereas the interior uses of Tachylite include Decorative aggregates and Interior decoration. Due to some exceptional properties of Porphyry and Tachylite, they have various applications in construction industry. The uses of Porphyry in construction industry include Construction aggregate and that of Tachylite include Cutting tool, Knives, Landscaping, Scrapers.
More about Porphyry and Tachylite
Here you can know more about Porphyry and Tachylite. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Porphyry and Tachylite consists of mineral content and compound content. The mineral content of Porphyry includes Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica and mineral content of Tachylite includes Feldspar, Olivine. You can also check out the list of all Igneous Rocks. When we have to compare Porphyry vs Tachylite, the texture, color and appearance plays an important role in determining the type of rock. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas, Tachylite is available in black, dark brown colors. Appearance of Porphyry is Dull and that of Tachylite is Glassy. Properties of rock is another aspect for Porphyry vs Tachylite. The hardness of Porphyry is 6-7 and that of Tachylite is 5.5. The types of Porphyry are Rhomb Porphyry whereas types of Tachylite are Volcanic glass. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Porphyry is white while that of Tachylite is vermilion. The specific heat capacity of Porphyry is 0.71 kJ/Kg K and that of Tachylite is 0.56 kJ/Kg K. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Porphyry is heat resistant, impact resistant whereas Tachylite is heat resistant, impact resistant, wear resistant.