Diabase formation took place millions of years ago. To warrant this effort, a special significance must have been placed on this particular type of rock. Image copyright iStockphoto / bonetiz. Diabase - Minerals.net Glossary of Terms. Photograph copyright iStockphoto / Stephen Barnes. The age criterion is not in use anymore, but both “dolerite” and “diabase” continue to be used. unaltered dolostone, the silicified dolostone, and the diabase in order to establish the mineral changes associated with the alteration. The Sierra Ancha olivine diabase has a high-alumina olivine basalt composition. Some igneous rocks have a complex cooling history that results in them containing grains of distinctly different crystal sizes. When cut and polished, this diabase can serve as an attractive architectural stone. It was a German geologist Harry Rosenbusch in 1877 who decided to introduce the age criterion and possibly created a problem that persists to this day. to be much more silicic than the diabase sills, and, therefore, it was concluded that they probably were not emplaced during the same phase of igneous activity. The term “microgabbro” is sometimes used to refer to such rocks. It was Brongniart himself who decided to abandon the term in 1827. The difference between basalt, diabase, and gabbro is in their grain size - which was determined by their cooling rates. Diabase can also be cut for use as ornamental stone for countertops, facing stone on buildings, and paving. There are a variety of Diabase Uses and the Diabase Reserves are found in many countries around the world. Although the mineral species present in diabase often have perfect cleavage, when they are present in tiny interlocking grains, the cleavage is usually not an important durability concern when the rock is used as a construction material. The two words are synonyms. Here are two facts about diabase and its commercial use: 1) The plagioclase in diabase is often of the labradorite variety. (FRL) - First Recorded Locality for everything else (eg varieties). The 2.21 Ga Nipissing diabase sills intrude the Huronian Supergroup of the Southern Province. Diabase is the preferred name in North America, while dolerite is the preferred name in the rest of English-speaking world, where … Diabase: A hand specimen of diabase approximately ten centimeters across. Giga-fren . As originally applied by Brongniart in 1807, the term corresponded to what is now recognized as diorite. It commonly occurs as tabular bodies (dikes and sills) intruded into surrounding rocks. In the United States, a syn. Most of the remainder is made up of pyroxene minerals (usually augite). Tenerife, Canary Islands. These rocks, with large crystals (known as "phenocrysts") suspended in a matrix of fine crystals (known as "groundmass"), often have a cooling history similar to the following description: Much diabase contains two distinctly different crystal sizes and is known as "diabase porphyry". The top part nicely displays a light gray weathering rind that is typical of diabase. 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. When you hear the name "diabase", you should examine the rock to confirm its identity, if the name of the rock is important. Altered diabase and albite diabase also have unusually calcium-rich pyroxenes. The width of the view is 14 cm. Texture: Occasionally ophitic texture can be distinguished in hand specimen. Diabase (dolerite) is a dark-colored igneous rock. Glossary of Terms. Brown spots are left by sea animals that were attached to the rock. White phenocrysts are plagioclase and black phenocrysts are pyroxene crystals. The fine-grained texture of diabase makes identification in the field or in a classroom a difficult undertaking. - World class for species or very significant. b) Architectural Stone: special-shape pieces used as stair treads, window lintels, window sills, counter tops, flooring tiles, facing stone, columns, etc. Explanations, illustrations, and photos of these structures can be found in this article. An igneous rock composed of minerals with two distinctly different crystal sizes is known as a porphyry. Width of the view is about 25 cm. The thin sections are examined using a 'petrographic microscope', which permits viewing under ordinary and under polarized light. Several samples were collected and analyzed in hand sample, in thin section, and using X-Ray Diffraction. Diabase is actually a variety of gabbro which consists mainly of labradorite feldspar, augite, magnetite, and olivine. In addition, dissolution rates of more crystalline rocks such as diabase may be slower than less crystalline rocks such as basalt, although the rates have been shown to be similar between glass and minerals of similar composition (e.g.Hamilton et al., 2000, Wolff-Boenisch et al., 2006). This sample is taken from a drillcore. The rock is 8 cm in length. According to him, only rocks of pre-Tertiary (pre-Cenozoic) age were named diabase. So, an initially black construction stone can alter to a chalky white, gray, or tan color. - Indicates mineral may be doubtful at this locality. 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. 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. A contact between basalt (on the left) and dolerite in Cyprus. d) Monument Stone: dimensional stone cut for use as monuments, burial markers, gateways, directories, memorials, etc.