Definition
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Comendite is a hard, peralkaline igneous rock, a type of light blue grey rhyolite
Origin
Romania and Moldova, Europe
Italy
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
Comendite derives its name from the area of Le Commende on San Pietro Island in Italy
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Hard Rock
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Medium Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Porphyritic
Color
Bluish - Grey, Brown, Grey, Light to Dark Grey
Blue, Bluish - Grey
Durability
Durable
Durable
Appearance
Vesicular
Foliated
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Countertops, Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, Paving Stone, Garden Decoration
As Building Stone, As Facing Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Raw material for the manufacture of mortar
Antiquity Uses
Artifacts
Artifacts
Commercial Uses
Commemorative Tablets, Creating Artwork
Cemetery Markers
Types
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Rhyolite
Features
Host Rock for Lead, Is one of the oldest rock
Very fine grained rock, It is One of the Oldest, Strongest and Hardest Rock
Archaeological Significance
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.
Comendite is a type of Igneous rock which is formed due to cooling and solidification of lava or magma. It may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Mineral Content
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Albite, Amphibole, Quartz
Compound Content
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Al, Fe, Potassium Oxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
Cataclastic 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, Water Erosion
Grain Size
Medium to Fine Coarse Grained
Medium Grained
Fracture
Conchoidal
Pervasive
Streak
White
Bluish Black
Porosity
Less Porous
Highly Porous
Luster
Subvitreous to Dull
Dull
Specific Gravity
2.86-2.87
2.38
Transparency
Translucent
Opaque
Density
2.77-2.771 g/cm3
-9999 g/cm3
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Europe
France, Greece, Romania, Scotland, Spain
Italy
Deposits in Western Continents
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
-
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
Queensland