Dacite and Gneiss
Definition
Definition
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks
History
Origin
Romania and Moldova, Europe
Unknown
Discoverer
Unknown
Unknown
Etymology
From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described
From the Middle High German verb gneist (to spark; so called because the rock glitters)
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Hard Rock
Family
Group
Volcanic
Not Applicable
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Texture
Aphanitic to Porphyritic
Banded, Foliated, Platy
Color
Bluish - Grey, Brown, Grey, Light to Dark Grey
Black, Brown, Pink, Red, White
Maintenance
Less
More
Durability
Durable
Durable
Water Resistant
No
Yes
Scratch Resistant
No
Yes
Stain Resistant
No
Yes
Wind Resistant
No
Yes
Acid Resistant
No
No
Appearance
Vesicular
Foliated
Uses
Architecture
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Countertops, Decorative Aggregates, Flooring, Interior Decoration
Exterior Uses
As Building Stone, Paving Stone, Garden Decoration
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
As Dimension Stone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts
Artifacts
Other Uses
Commercial Uses
Commemorative Tablets, Creating Artwork
Cemetery Markers, Jewelry, Tombstones, Used in aquariums
Types
Types
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.
Features
Host Rock for Lead, Is one of the oldest rock
Generally rough to touch, Is one of the oldest rock
Archaeological Significance
Monuments
Not Yet Used
Used
Famous Monuments
Not Applicable
Konark Sun Temple in India, Washington Monument, US
Sculpture
Not Yet Used
Not Yet Used
Famous Sculptures
Not Applicable
Not Applicable
Pictographs
Used
Not Used
Petroglyphs
Used
Not Used
Figurines
Not Yet Used
Not Yet Used
Fossils
Absent
Absent
Formation
Formation
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.
Gneiss is a high grade metamorphic rock i.e. it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of Gneiss forms from volcanic rock, shale or granitie.
Composition
Mineral Content
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon
Compound Content
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Aluminium Oxide, NaCl, CaO, Iron(III) Oxide, FeO, Potassium Oxide, Magnesium Carbonate, MgO, MnO, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Transformation
Metamorphism
Yes
Yes
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
Impact Metamorphism
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Mechanical Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion
Chemical Erosion, Coastal Erosion, Sea Erosion
Properties
Physical Properties
Hardness
2-2.25
7
Grain Size
Medium to Fine Coarse Grained
Medium to Coarse Grained
Fracture
Conchoidal
Irregular
Streak
White
White
Porosity
Less Porous
Very Less Porous
Luster
Subvitreous to Dull
Dull
Compressive Strength
Not Available
125.00 N/mm2
17
Cleavage
Perfect
Poor
Toughness
Not Available
1.2
Specific Gravity
2.86-2.87
2.5-2.7
Transparency
Translucent
Translucent to Opaque
Density
2.77-2.771 g/cm3
2.6-2.9 g/cm3
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K
10
Not Available
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant
Reserves
Deposits in Eastern Continents
Asia
Not Yet Found
China, India, Iran, Iraq, Kazakhstan, Kyrgyzstan, Mongolia, Russia
Africa
Not Yet Found
Cameroon, Ethiopia, Ghana, Kenya, Madagascar, Morocco, Mozambique, Namibia, Nigeria, Tanzania, Togo
Europe
France, Greece, Romania, Scotland, Spain
Albania, Austria, Bosnia and Herzegovina, Finland, France, Georgia, Germany, Hungary, Italy, Kosovo, Monaco, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Switzerland, Ukraine, United Kingdom
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
USA
Canada, Costa Rica, Cuba, Mexico, Panama, USA
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Venezuela
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
New South Wales, New Zealand, Queensland, Victoria
All about Dacite and Gneiss Properties
Know all about Dacite and Gneiss properties here. All properties of rocks are important as they define the type of rock and its application. Dacite belongs to Igneous Rocks while Gneiss belongs to Metamorphic Rocks.Texture of Dacite is Aphanitic to Porphyritic whereas that of Gneiss is Banded, Foliated, Platy. Dacite appears Vesicular and Gneiss appears Foliated. The luster of Dacite is subvitreous to dull while that of Gneiss is dull. Dacite is available in bluish - grey, brown, grey, light to dark grey colors whereas Gneiss is available in black, brown, pink, red, white colors. The commercial uses of Dacite are commemorative tablets, creating artwork and that of Gneiss are cemetery markers, jewelry, tombstones, used in aquariums.
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