What are the properties of dolerite?
Dolerite. Fine grained, ophitic texture. Primary minerals – plagioclase, pyroxene, hornblende and quartz. Acicular and lath-like plagioclase, equant grains of pyroxene – some alteration to chlorite along cleavage and fissures.
What rock is jersey made of?
Jersey is famous for its granites, which have been favoured as a building material for thousands of years. These major intrusive or ‘plutonic’ rocks were formed between 580 and 480 million years ago by molten rock cooling and solidifying between the Earth’s surface.
What is the hardness of dolerite?
The hardness values (Hv), which are average readings, show that there is overlap in dolerite and hornfels Hv values (Fig. The Hv values achieved during our tests ranged between 551 and 210 for hornfels and between 538 and 272 for dolerite. The higher the Hv value the harder the rock.
What is dolerite rock?
Dolerite is the name given to the medium-grained intrusive basic igneous rock commonly found in dykes and sills; in North America and continental Europe it is often referred to as diabase, but many authors restrict this term to altered dolerite.
Is dolerite a hard rock?
diabase, also called Dolerite, fine- to medium-grained, dark gray to black intrusive igneous rock. It is extremely hard and tough and is commonly quarried for crushed stone, under the name of trap.
What is interesting about the diabase’s environment of formation?
1) The plagioclase in diabase is often of the labradorite variety. Diabase from some quarries contains abundant crystals of labradorite that are capable of producing colorful reflections known as “labradorescence”. When cut and polished, this diabase can serve as an attractive architectural stone.
Is Jersey a volcano?
Jersey is the sort of place that appeals to geologists. Millions of years ago it was in an area near a volcano. The lava which spewed forth formed the dark, mauve coloured rocks peculiar to Jersey. These rock formations around the coastline tell the story of how the island was formed in ancient times.
How hard is dolerite rock?
diabase, also called Dolerite, fine- to medium-grained, dark gray to black intrusive igneous rock. It is extremely hard and tough and is commonly quarried for crushed stone, under the name of trap. With increase in grain size, diabase may pass into gabbro.
What is the difference between dolerite and basalt?
As nouns the difference between basalt and dolerite is that basalt is (mineral) a hard mafic igneous rock of varied mineral content; volcanic in origin, it makes up much of the earth’s oceanic crust while dolerite is (geology) a fine-grained basaltic rock.
What are the essential minerals of dolerite?
Their essential minerals are those of basalt, viz. olivine, augite and plagioclase felspar, while hornblende, ilmenite, apatite and biotite are their commonest accessory ingredients.
Is dolerite similar to basalt?
əˌbeɪs/), also called dolerite (/ˈdɒl. əˌraɪt/) or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro.
What kind of rock is a dolerite?
Dolerite is a dark igneous rock. It is a mafic rock, containing magnesium and iron, often in form of olivine. Like other mafic rocks, it is relatively low in silica content. It is a medium grained igneous rock, and can be dark grey or black with greenish shades in colour.
What makes up diabase and what makes dolerite?
Diabase. Diabase is composed of plagioclase feldspar (mostly labradorite) and pyroxene ( augite ). The crystals that make up dolerite are usually visible to the naked eye, but sometimes porphyritic rocks of basaltic composition with pyroxene and especially plagioclase phenocrysts are also named that way.
How are the minerals in the dolerite family distributed?
THE DIABASE (DOLERITE) FAMILY. Quartz, calcite, epidote, chlorite and serpentine are common secondary minerals; and these minerals are often distributed in veins and nests through the rocks. The structure of the dolerites is characteristically ophitic; but in some cases a granular structure prevails.
Where can you find dolerite in Northern Ireland?
Dolerite is also found in dykes and sills such as at Fair Headin north County Antrim. Much of the dolerite found in these places has a greenish tinge because of the presence of the mineral olivine.
https://www.youtube.com/watch?v=JF4Vvmprlbw