Definition
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth
Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock
Discoverer
Obsius
Van Tooren
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Greek tephra, ashes from Indo-European base, to burn
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Other Categories
Opaque Rock
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Glassy
Aphanitic to Porphyritic
Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Black, Brown, Green, Grey, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Shiny
Vesicular
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Flooring, Homes, Interior Decoration
Exterior Uses
Garden Decoration
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
Other Architectural Uses
-
Curbing
Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
Landscaping
Medical Industry
Surgery
-
Antiquity Uses
Artifacts, Jewellery
Artifacts, Sculpture
Commercial Uses
Creating Artwork, Mirror, Used in aquariums
Production of Lime, Soil Conditioner
Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Igneous rock
Features
Blocks negativity, Helps to protect against depression
Host Rock for Lead
Archaeological Significance
Formation
When the lava is released from volcano, it undergoes a very rapid cooling which freezes the mechanisms of crystallization. The result is a volcanic glass with a uniform smooth texture.
Tephrite 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
-
Alkali feldspar, Nepheline, Plagioclase, Pyroxene
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
CaO, Carbon Dioxide, MgO, Silicon Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion
Grain Size
-
Medium to Fine Coarse Grained
Fracture
Conchoidal
Uneven
Streak
White
Bluish Black
Porosity
Very Less Porous
Very Less Porous
Luster
Vitreous
Subvitreous to Dull
Cleavage
-
Crenulation and Pervasive
Specific Gravity
2.6-2.7
2.86
Transparency
Translucent
Opaque
Density
2.6 g/cm3
2.8-2.9 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
Afghanistan, Indonesia, Japan, Russia
-
Africa
Kenya
Namibia, Uganda
Europe
Greece, Hungary, Iceland, Italy, Turkey
Germany, Hungary, Italy, Portugal, Spain
Deposits in Western Continents
North America
Canada, Mexico, USA
USA
South America
Argentina, Chile, Ecuador, Peru
-
Deposits in Oceania Continent
Australia
New Zealand
New Zealand, Western Australia
Obsidian vs Tephrite 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. Obsidian vs Tephrite characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Obsidian and Properties of Tephrite. Learn more about Obsidian vs Tephrite in the next section. The interior uses of Obsidian include Decorative aggregates and Interior decoration whereas the interior uses of Tephrite include Decorative aggregates, Flooring, Homes and Interior decoration. Due to some exceptional properties of Obsidian and Tephrite, they have various applications in construction industry. The uses of Obsidian in construction industry include Arrowheads, Cutting tool, Knives, Scrapers, Spear points and that of Tephrite include Landscaping.
More about Obsidian and Tephrite
Here you can know more about Obsidian and Tephrite. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Obsidian and Tephrite consists of mineral content and compound content. The mineral content of Obsidian includes and mineral content of Tephrite includes Alkali feldspar, Nepheline, Plagioclase, Pyroxene. You can also check out the list of all Igneous Rocks. When we have to compare Obsidian vs Tephrite, the texture, color and appearance plays an important role in determining the type of rock. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas, Tephrite is available in black, brown, green, grey, white colors. Appearance of Obsidian is Shiny and that of Tephrite is Vesicular. Properties of rock is another aspect for Obsidian vs Tephrite. The hardness of Obsidian is 5-5.5 and that of Tephrite is 6.5. The types of Obsidian are Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian whereas types of Tephrite are Igneous rock. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Obsidian is white while that of Tephrite is bluish black. The specific heat capacity of Obsidian is 0.92 kJ/Kg K and that of Tephrite is 0.92 kJ/Kg K. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Obsidian is heat resistant, impact resistant whereas Tephrite is heat resistant, impact resistant.