What type of rock can be dated with radiometric methods? Solution the metamorphic rock and Igneous rock & melt, all are vey slowly cooling and we can measure radioactivity decay unless or until it cool down below it’s the closure temperature.and more frequently used radiometric dating technique are depending on breakdown of the Potassium [40K] to -argon [40Ar]. sharp measurement of 40K to-- 40Ar amount in the igneous rock can tell you the real amount of time has been passed since this rock crystallized.for the sedimentary rocks we used Carbon-14 method for young rock( >50,00 years old rock) . This method is depend upon uptake of the naturally occured radioactive isotope like carbon-14,when living organism dead than stop accumulating carbon-14 atomes in body,over a time dead living things incorprated into the sedimentary rock, and geo-scientist calculate radiometric dating by using this carbon-14 atoms.this method used to measure the age of meteorites, Earth , ages of fossils, Moon, also early man, ages of mineral deposits, timing of glaciations, recurrence the rates of volcanic, earthquakes & eruptions Geologists scientist use this radiometric dating method to estimate or determine that how long ago back rocks were formed, & give information of ages of the fossils that contained within rocks. Naturally occurring various radioactive elements in the universe, and we know that Radioactive atoms are generally inherently unstable ,in radioactive \"large atoms\" decay into the stable small daughter atoms.in general When the molten rock cool & forming rock are know as igneous rocks a lot of radioactive atom were trapped inside the rock. than they starte decaying at the perticular expected rate. By determine the number of unstable atoms are left in rock & compare to the number of stable molecule of daughter atoms in a rock, geologist can be estimated the amount of the time is over since the perticularly rock formed.but the Fossils are frequently found in sedimentary rock,& not in the igneous rock. Sedimentary rocks can be use to dated a radioactively,carbon, but the problem is carbon decays vey quickly, this method can only work for the younger rocks age about 50 thousand years. So that in order to measure or date rock & older fossils, geologist scientists used layer of the volcanic ash & igneous rock below and above the fossil.geo- Scientists date the igneous rock by using elements which slow to decay, like uranium & potassium..