What is the special features of the rock chert?

Any good rockhound is bound to come across a rock that he or she has trouble identifying, especially if the location of where the rock was found is unknown. To identify a rock, think like a geologist and examine its physical characteristics for clues. The following tips and tables contain characteristics that will help you identify the most common rocks on earth.

Rock Identification Tips

First, decide whether your rock is igneous, sedimentary or metamorphic.

Igneous rocks such as granite or lava are tough, frozen melts with little texture or layering. Rocks like these contain mostly black, white and/or gray minerals.Sedimentary rocks such as limestone or shale are hardened sediment with sandy or clay-like layers (strata). They are usually brown to gray in color and may have fossils and water or wind marks.Metamorphic rocks such as marble are tough, with straight or curved layers (foliation) of light and dark minerals. They come in various colors and often contain glittery mica.

Next, check the rock's grain size and hardness.

Grain Size: Coarse grains are visible to the naked eye, and the minerals can usually be identified without using a magnifier. Fine grains are smaller and usually cannot be identified without using a magnifier.Hardness: This is measured with the Mohs scale and refers to the minerals contained within a rock. In simple terms, hard rock scratches glass and steel, usually signifying the minerals quartz or feldspar, which has a Mohs hardness of 6 or higher. Soft rock does not scratch steel but will scratch fingernails (Mohs scale of 3 to 5.5), while very soft rock won't even scratch fingernails (Mohs scale of 1 to 2). 

Rock Identification Chart

Once you've determined what type of rock you've got, look closely at its color and composition. This will help you identify it. Start in the left column of the appropriate table and work your way across. Follow the links to pictures and more information. 

Igneous Rock Identification

Grain SizeUsual Typefinedarkglassy appearancelava small bubbleslava froth from sticky lavaPumicefinedarkmany large bubbleslava froth from fluid lavaScoriafine or mixedlightcontains quartzhigh-silica lavaFelsitefine or mixedmediumbetween felsite and basaltmedium-silica lavaAndesitefine or mixeddarkhas no quartzlow-silica lavaBasaltmixedany colorlarge grains in fine-grained matrixlarge grains of feldspar, quartz, pyroxene or range of color and grain sizefeldspar and quartz with minor mica, amphibole or granite but without quartzfeldspar with minor mica, amphibole or to mediumlittle or no alkali feldsparplagioclase and quartz with dark to darklittle or no quartzlow-calcium plagioclase and dark to darkno quartz; may have olivinehigh-calcium plagioclase and dark ; always has olivineolivine with amphibole and/or pyroxene with olivine and least 90 percent olivineDunitevery coarseany colorusually in small intrusive bodiestypically graniticPegmatite

 

Sedimentary Rock Identification

HardnessGrain SizeCompositionOtherRock Typehardcoarseclean quartzwhite to and feldsparusually very coarseArkosehard or softmixedmixed sediment with rock grains and claygray or dark and "dirty"Wacke/
Graywackehard or softmixedmixed rocks and sedimentround rocks in finer sediment matrixConglomeratehard or
softmixedmixed rocks and sedimentsharp pieces in finer sediment fine sand; no clayfeels gritty on fizzing with acidChertsoftfineclay mineralssplits in ; burns with tarry with acidLimestonesoftcoarse or finedolomiteno fizzing with acid unless powderedDolomite rocksoftcoarsefossil shellsmostly piecesCoquinavery softcoarsehalitesalt tasteRock Saltvery softcoarsegypsumwhite, tan or pinkRock Gypsum

 

Metamorphic Rock Identification

FoliationGrain SizeUsual ColorOtherRock soft; greasy ; strong ; massive ; crinkly dark and lightcrushed and stretched fabric; deformed large dark and lightwrinkled foliation; often has large "melted" ; shiny, mottled or coarsedarkdull

Tbh irdk srry :-(

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.