Definition
Very fine grained fault rock which is composed of glassy matrix that often contains inclusions of wall-rock fragments.
Felsite is a very fine grained volcanic rock that may or may not contain larger crystals and light colored rock that typically requires petrographic examination or chemical analysis for more precise definition
Discoverer
Unknown
Unknown
Etymology
From pseudo- + tachylite, a glassy rock generated by frictional heat within faults.
From English feldspar and -ite
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Group
Not Applicable
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Quench
Arborescent Patterned, Vitreous
Color
Black, Brown, Colourless, Green, Grey, Pink, White
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull and Soft
Layered, Banded, Veined and Shiny
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Decorative Aggregates, Flooring, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration
Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Cement Manufacture, for Road Aggregate, Making natural cement
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
Medical Industry
Not Yet Used
Surgery
Antiquity Uses
Artifacts, Monuments
Artifacts
Commercial Uses
Creating Artwork, Gemstone
Mirror, Jewelry
Types
Not Available
Not Available
Features
Host Rock for Lead
Available in Lots of Colors and Patterns, Clasts are smooth to touch, Splintery, Very fine grained rock
Archaeological Significance
Monuments
Used
Not Yet Used
Famous Monuments
Data Not Available
Not Applicable
Sculpture
Not Yet Used
Not Yet Used
Famous Sculptures
Not Applicable
Not Applicable
Pictographs
Not Used
Used
Petroglyphs
Not Used
Used
Figurines
Not Yet Used
Not Yet Used
Formation
Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Pseudotachylite is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.
Felsite 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
Iron Oxides, Pyroxene, Quartz, Stishovite, Sulfides
Feldspar, Iron Oxides
Compound Content
Carbon Dioxide, Silicon Dioxide, Sulfur Dioxide, Sulphur
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Burial Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Not Applicable
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Not Applicable
Chemical Erosion, Glacier Erosion, Water Erosion
Grain Size
Very fine-grained
Fine Grained
Fracture
Uneven
Conchoidal
Streak
Light to dark brown
White
Porosity
Less Porous
Very Less Porous
Cleavage
Irregular
Non-Existent
Toughness
Not Available
Not Available
Specific Gravity
2.46-2.86
2.6-2.7
Transparency
Transparent to Translucent
Translucent
Density
2.7-2.9 g/cm3
2.6 g/cm3
Resistance
Heat Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
South Korea
Afghanistan, Indonesia, Japan, Russia
Africa
Western Africa
Kenya
Europe
Great Britain, Switzerland
Greece, Hungary, Iceland, Italy, Turkey
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
Not Yet Found
Canada, Mexico, USA
South America
Not Yet Found
Argentina, Chile, Ecuador, Peru
Deposits in Oceania Continent
Australia
Central Australia, Western Australia
New Zealand
All about Pseudotachylite and Felsite Properties
Know all about Pseudotachylite and Felsite properties here. All properties of rocks are important as they define the type of rock and its application. Pseudotachylite belongs to Metamorphic Rocks while Felsite belongs to Igneous Rocks.Texture of Pseudotachylite is Quench whereas that of Felsite is Arborescent Patterned, Vitreous. Pseudotachylite appears Dull and Soft and Felsite appears Layered, Banded, Veined and Shiny. The luster of Pseudotachylite and Felsite is vitreous. Pseudotachylite is available in black, brown, colourless, green, grey, pink, white colors whereas Felsite is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Pseudotachylite are creating artwork, gemstone and that of Felsite are mirror, jewelry.