No they do no longer seem to be, as they do no longer seem to be clastic, and subsequently have no grains to be measured. Chemical (and biochemical) rocks fall into countless communities, in accordance with how they form and what their chemistry is (ta-dah). CARBONATES: those are composed of the mineral calcite (CaCO3 - calcium carbonate), and are subsequently all time-honored as carbonates. there are various varieties, they form by using the two chemical and biochemical procedures, and that they have a tendency to be mixed at the same time in countless combos interior the rocks. they're relatively significant and important. different CHEMICAL ROCKS: those rocks fall into 2 categories. Chert is a siliceous rock (composed of SiO2) that varieties from the recrystalized skeletons of animals (single celled radiolarians, and glass sponges) or single celled vegetation (diatoms, silicoflagellates). And besides the reality that the silica comes from skeletons to develop into chert it would desire to be chemically recrystallized, subsequently putting it interior the chemical class relatively than clastic (besides the undeniable fact that it truly is truly confusing once you're gaining knowledge of). Rock salt (halite; NaCl) and gypsum (CaSO4 . H2O) initially are dissolved interior the sea water, subsequently making the sea salty. while sea water evaporates in a closed section, at the same time with a lagoon, the salt concentration will become very extreme, supersaturated, and precipitates out. the technique is user-friendly in wasteland factors, with examples on the instant interior the pink Sea and lifeless Sea interior the middle East, the two fantastically saline.
There is an arguement whether organic sedimentary rocks such as fossiliferous limestones and coal are chemical sedimentary rocks or whether they are organic sedimentary rocks. I have taken this classification from pedia (reference quoted). A deficiency of this classification is that it excludes dolomites and phosphate rich rocks which are probably originally deposited as limestones are transformed due to magnesium rich or phosphate rich waters invading the in-situ rock during diagenesis. a) Biochemical sedimentary rocks Biochemical sedimentary rocks are created when organisms use materials dissolved in air or water to build their tissue. Examples include: i Most types of limestone are formed from the calcareous skeletons of organisms such as corals, molluscs, and foraminifera. ii Coal which forms as plants remove carbon from the atmosphere and combine with other elements to build their tissue. iii Deposits of chert formed from the accumulation of siliceous skeletons from microscopic organisms such as radiolaria and diatoms. b) Chemical sedimentary rocks Chemical sedimentary rock forms when mineral constituents in solution become supersaturated due to evaporation, and inorganically precipitate. These tend to form in a lagoonal environment where sea water can occasionally enter but cannot leave. Common chemical sedimentary rocks include oolitic limestone and rocks composed of evaporite minerals such as halite (rock salt), sylvite, barite and gypsum.
