Definition
Trachyte is a grey fine-grained volcanic rock which mainly consists of alkali feldspar
  
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
  
  
Discoverer
Alexandre Brongniart and René Just Haüy
  
Unknown
  
Etymology
From Greek trakhus rough’ or trakhutēs roughness
  
From the Middle High German verb gneist (to spark; so called because the rock glitters)
  
Class
Igneous Rocks
  
Metamorphic Rocks
  
Sub-Class
Durable Rock, Medium Hardness Rock
  
Durable Rock, Hard Rock
  
Family
  
  
Group
Volcanic
  
Not Applicable
  
Other Categories
Fine Grained Rock, Opaque Rock
  
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
  
Texture
Aphanitic to Porphyritic
  
Banded, Foliated, Platy
  
Color
Black, Brown, Dark Greenish - Grey, Green, Grey, Light to Dark Grey, White
  
Black, Brown, Pink, Red, White
  
Maintenance
Less
  
More
  
Durability
Durable
  
Durable
  
Water Resistant
Yes
  
Yes
  
Scratch Resistant
Yes
  
Yes
  
Stain Resistant
Yes
  
Yes
  
Wind Resistant
Yes
  
Yes
  
Acid Resistant
No
  
No
  
Appearance
Banded
  
Foliated
  
Architecture
  
  
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
  
Countertops, Decorative Aggregates, Flooring, Interior Decoration
  
Exterior Uses
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
  
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
  
Other Architectural Uses
Curbing
  
Curbing
  
Industry
  
  
Construction Industry
As Dimension Stone, Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Manufacture of Magnesium and Dolomite Refractories
  
As Dimension Stone
  
Medical Industry
Not Yet Used
  
Not Yet Used
  
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
  
Artifacts
  
Other Uses
  
  
Commercial Uses
Cemetery Markers, Creating Artwork
  
Cemetery Markers, Jewelry, Tombstones, Used in aquariums
  
Types
Not Available
  
Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.
  
Features
Available in Lots of Colors and Patterns, Is one of the oldest rock, Matrix variable
  
Generally rough to touch, Is one of the oldest rock
  
Archaeological Significance
  
  
Monuments
Used
  
Used
  
Famous Monuments
Data Not Available
  
Konark Sun Temple in India, Washington Monument, US
  
Sculpture
Used
  
Not Yet Used
  
Famous Sculptures
Data Not Available
  
Not Applicable
  
Pictographs
Used
  
Not Used
  
Petroglyphs
Used
  
Not Used
  
Figurines
Used
  
Not Yet Used
  
Fossils
Absent
  
Absent
  
Formation
Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. It is the volcanic equivalent of syenite rock and forms as a result of magmatic differentiation.
  
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
Augite, Biotite, Feldspar, Hornblade, Plagioclase, Quartz
  
Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon
  
Compound Content
Potassium Oxide, Sodium Oxide, 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
Cataclastic Metamorphism, Contact Metamorphism, Regional 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, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
  
Chemical Erosion, Coastal Erosion, Sea Erosion
  
Physical Properties
  
  
Hardness
6
  
7
  
Grain Size
Fine Grained
  
Medium to Coarse Grained
  
Fracture
Not Available
  
Irregular
  
Streak
White
  
White
  
Porosity
Less Porous
  
Very Less Porous
  
Luster
Metallic
  
Dull
  
Compressive Strength
150.00 N/mm2
  
14
125.00 N/mm2
  
17
Cleavage
Not Available
  
Poor
  
Toughness
Not Available
  
1.2
  
Specific Gravity
2.7
  
2.5-2.7
  
Transparency
Opaque
  
Translucent to Opaque
  
Density
2.43-2.45 g/cm3
  
2.6-2.9 g/cm3
  
Thermal Properties
  
  
Resistance
Heat Resistant, Impact Resistant, Wear Resistant
  
Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant
  
Deposits in Eastern Continents
  
  
Asia
China, India, Iran, Saudi Arabia, Sri Lanka, Taiwan, Thailand, Turkey, Vietnam
  
China, India, Iran, Iraq, Kazakhstan, Kyrgyzstan, Mongolia, Russia
  
Africa
Angola, Egypt, Madagascar, Namibia, Nigeria, South Africa
  
Cameroon, Ethiopia, Ghana, Kenya, Madagascar, Morocco, Mozambique, Namibia, Nigeria, Tanzania, Togo
  
Europe
Bulgaria, England, Germany, Norway, Romania, Switzerland
  
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
Brazil, Chile
  
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Venezuela
  
Deposits in Oceania Continent
  
  
Australia
New Zealand, Queensland, South Australia, Western Australia
  
New South Wales, New Zealand, Queensland, Victoria