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Types of Sedimentary Rocks

Sedimentary rocks form from sediment, shells and dissolved minerals that were deposited in layers and cemented over time. Clastic rocks such as sandstone, shale and conglomerate are made of grains; chemical and biological rocks such as limestone, chalk, coal and rock salt precipitated or accumulated from water and organisms.

Look for layering, rounded or angular grains, fossils, and a gritty or earthy feel. A drop of vinegar fizzes on the carbonate members.

Mohs hardness in this group runs from 1 to 7.

Also browse:Types of Igneous RocksTypes of Metamorphic RocksMinerals A to ZGemstonesMetals & Alloys

All sedimentary rocks (29)

Mookaite specimen: yellow and red sedimentary rockMookaiteMohs 6.5 · White streakSandstone specimen: tan and brown sedimentary rockSandstoneMohs 6 · Variable; test individual minerals streakLimestone specimen: white and gray sedimentary rockLimestoneMohs 3 · White streakRock Salt specimen: clear and white sedimentary rockRock SaltMohs 2.5 · White streakDolostone specimen: tan and gray sedimentary rockDolostoneMohs 3.5 · White streakSiltstone specimen: gray and tan sedimentary rockSiltstoneMohs 3.5 · Variable; often light gray to brown streakIronstone specimen: brown and red brown sedimentary rockIronstoneMohs 4 · Brown to reddish brown streakDiatomite specimen: white and cream sedimentary rockDiatomiteMohs 1.5 · White streakLaterite specimen: red and orange sedimentary rockLateriteMohs 4 · Red brown to yellow brown streakEvaporite specimen: white and clear sedimentary rockEvaporiteMohs 2.5 · White streakOolite specimen: white and cream sedimentary rockOoliteMohs 3 · White to light-colored streakGraywacke specimen: dark gray and greenish gray sedimentary rockGraywackeMohs 6 · Gray to dark gray streakCaliche specimen: white and cream sedimentary rockCalicheMohs 3 · White to pale tan streakMarl specimen: gray and cream sedimentary rockMarlMohs 2.5 · White to light gray streakArkose specimen: pink and red sedimentary rockArkoseMohs 6 · Variable; usually light-colored streakBanded Iron Formation specimen: red and reddish brown sedimentary rockBanded Iron FormationMohs 5–7 · Reddish brown (from hematite-rich layers) streakBreccia specimen: sedimentary rockBrecciaMohs 3.5 · Variable; test individual minerals streakChalk specimen: white and pale gray sedimentary rockChalkMohs 1–2 · White streakChert specimen: gray and white sedimentary rockChertMohs 6.5–7 · Waxy to dullClaystone specimen: gray and red sedimentary rockClaystoneMohs 2–3 · Dull, earthyCoal specimen: black and brownish black sedimentary rockCoalMohs 1–2.5 · Black to brownish black streakConglomerate specimen: variegated and gray sedimentary rockConglomerateMohs 3–7 · Variable; dull matrix to vitreous clastsCoquina specimen: white and tan sedimentary rockCoquinaMohs 3–4 · DullDolomite specimen: white and gray sedimentary rockDolomiteMohs 3.5–4 · White streakFlint specimen: black and dark gray sedimentary rockFlintMohs 6.5–7 · Waxy to dull, glassy on fresh fractureMudstone specimen: gray and brown sedimentary rockMudstoneMohs 2–3 · Dull, earthyShale specimen: gray and black sedimentary rockShaleMohs 2–3 · Dull to earthy (slightly sub-vitreous if micaceous)Shungite specimen: black and dark gray sedimentary rockShungiteMohs 3.5 · Black streakTravertine specimen: white and cream sedimentary rockTravertineMohs 3–4 · White streak

Frequently asked questions

What are the most common sedimentary rocks?

The most searched sedimentary rocks in the StoneSnap database are Mookaite, Sandstone, Limestone, Rock Salt, and Dolostone.

How do you identify sedimentary rocks?

Start with luster and color, then bracket the Mohs hardness with a scratch test and check the streak on unglazed porcelain. Mohs hardness in this group runs from 1 to 7. Each entry below lists the diagnostic properties and its common look-alikes.

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