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
Greywacke is defined as a dark coarse-grained sandstone rock which contains more than 15 per cent clay
Discoverer
Obsius
Unknown
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From German Grauwacke, from grau grey + wacke
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock
Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Beige, Black, Brown, Cream, Dark Brown, Green, Grey, Light Green, Light to Dark Grey, Pink, Red, White, Yellow
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Floor Tiles, Flooring, Homes, Interior Decoration
Exterior Uses
Garden Decoration
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
Other Architectural Uses
-
Curbing, Whetstones
Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Raw material for the manufacture of mortar
Medical Industry
Surgery
-
Antiquity Uses
Artifacts, Jewellery
Artifacts, Sculpture, Small Figurines
Commercial Uses
Creating Artwork, Mirror, Used in aquariums
As armour rock for sea walls, Petroleum reservoirs, Sea Defence, Tombstones
Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Greywacke
Features
Blocks negativity, Helps to protect against depression
Available in Lots of Colors and Patterns, Generally rough to touch, Non-vesicular, Veined
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.
Graywacke rock is a type of sedimentary rock, which is also known as immature sandstone, which is indurated, dark grey and consisting of poorly sorted angular to sub-angular, sand-sized grains.
Mineral Content
-
Augite, Biotite, Calcite, Chlorite, Clay, Clay Minerals, Feldspar, Micas, Muscovite or Illite, Plagioclase, Pyroxene, Quartz
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Aluminium Oxide, NaCl, CaO, Chromium(III) Oxide, Iron(III) Oxide, FeO, Potassium Oxide, Magnesium Carbonate, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
-
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Coastal Erosion, Sea Erosion, Wind Erosion
Grain Size
-
Angular and Fine
Fracture
Conchoidal
Conchoidal
Porosity
Very Less Porous
Highly Porous
Specific Gravity
2.6-2.7
2.2-2.8
Transparency
Translucent
Opaque
Density
2.6 g/cm3
2.6-2.61 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
Afghanistan, Indonesia, Japan, Russia
China, India, Kazakhstan, Mongolia, Russia, Uzbekistan
Africa
Kenya
Namibia, Nigeria, South Africa
Europe
Greece, Hungary, Iceland, Italy, Turkey
Austria, Denmark, Germany, Great Britain, Netherlands, Norway, Poland, Sweden, Switzerland, United Kingdom
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, USA
South America
Argentina, Chile, Ecuador, Peru
Brazil
Deposits in Oceania Continent
Australia
New Zealand
New South Wales, New Zealand
All about Obsidian and Greywacke Properties
Know all about Obsidian and Greywacke properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Greywacke belongs to Sedimentary Rocks.Texture of Obsidian is Glassy whereas that of Greywacke is Clastic. Obsidian appears Shiny and Greywacke appears Dull. The luster of Obsidian is vitreous while that of Greywacke is dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Greywacke is available in beige, black, brown, cream, dark brown, green, grey, light green, light to dark grey, pink, red, white, yellow colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Greywacke are as armour rock for sea walls, petroleum reservoirs, sea defence, tombstones.