Definition
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Ignimbrite is a volcanic rock consisting mainly of pumice fragments, formed by the consolidation of material deposited by pyroclastic flows
Origin
Romania and Moldova, Europe
New Zealand
Discoverer
Unknown
Patrick Marshall
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 Latin ignis fire + imber, imbr- shower of rain, storm cloud + -ite
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Aphanitic
Color
Bluish - Grey, Brown, Grey, Light to Dark Grey
Beige, Black, Brown, Grey, Pink, White
Durability
Durable
Durable
Appearance
Vesicular
Dull, Vesicular and Foilated
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Decorative Aggregates, Floor Tiles, Homes, Interior Decoration
Exterior Uses
As Building Stone, Paving Stone, Garden Decoration
As Building Stone, Garden Decoration, Office Buildings, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
Building houses or walls, Construction Aggregate
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture, Small Figurines
Commercial Uses
Commemorative Tablets, Creating Artwork
Cemetery Markers, Commemorative Tablets, Creating Artwork
Types
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Pyroclastic rock
Features
Host Rock for Lead, Is one of the oldest rock
Always found as volcanic pipes over deep continental crust
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.
Ignimbrites are formed from very poorly sorted mixture of volcanic ash or tuff and pumice lapilli, commonly with scattered lithic fragments.
Mineral Content
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Apatite, Biotite, Calcite, Chlorite, Feldspar, Hematite, Hornblade, Ilmenite, Magnetite, Olivine, Pyroxene, Quartz
Compound Content
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Ca, NaCl
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
Burial Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering
Types of Erosion
Chemical Erosion
Chemical Erosion, Coastal Erosion
Grain Size
Medium to Fine Coarse Grained
Fine Grained
Fracture
Conchoidal
Uneven
Porosity
Less Porous
Highly Porous
Luster
Subvitreous to Dull
Vitreous to Dull
Specific Gravity
2.86-2.87
2.73
Transparency
Translucent
Opaque
Density
2.77-2.771 g/cm3
1-1.8 g/cm3
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
-
Afghanistan, Armenia, Azerbaijan, Burma, Cambodia, China, India, Indonesia, Iran, Japan, Malaysia, Mongolia, Nepal, North Korea, Pakistan, Saudi Arabia, Syria, Taiwan, Thailand, Turkey, Vietnam, Yemen
Africa
-
Cameroon, Cape Verde, Chad, Djibouti, Eritrea, Ethiopia, Kenya, Libya, Madagascar, Nigeria, Rwanda, South Africa, Sudan, Tanzania, Uganda
Europe
France, Greece, Romania, Scotland, Spain
France, Georgia, Germany, Greece, Iceland, Italy, Netherlands, Poland, Portugal, Spain, United Kingdom
Others
-
Antarctica, Hawaii Islands
Deposits in Western Continents
North America
USA
Canada, Costa Rica, Panama, USA
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
Central Australia, Western Australia