(1991) first proposed that dating of barite is possible.Barite crystals are formed when submarine hydrothermal fluid containing Ba is mixed with sea water containing sulfate anions.The obtained efficiency values (the slopes of the tangents) are listed in Table 1. 1.4 to be 0.053 ± 0.006 for HPD#1621R07 (the young natural sample), to be 0.102 ± 0.022 for HPD#1358R03 (the natural old sample), and to be 0.017 ± 0.001 for the synthetic sample as shown in Table 1. The efficiency is the slope of the tangent at the point where signal intensity is zero on the saturating exponential curve of the dose response.The k -values are obtained as the ratio of the efficiencies to He ion implantation and to the gamma ray irradiation.The samples were soaked in 12M hydrochloric acid, left for approximately 24 hours. Finally, after rinsing in distilled water, the sample was filtered and dried. An X-ray diffraction study was made to confirm that the grains are pure barite. Another barite was synthesized by mixing barium chloride (Ba Cl 2Na Cl Aqueous solutions of 300 ml with 0.32 mol/L of barium chloride and of 300 ml with 0.32 mol/L of sodium sulfate, are mixed together at room temperature to have barium sulfate precipitated.The above powder barite samples of two types (natural and synthetic) were deposited on aluminum plates in deionized water with an area of 2 cm Co gamma ray source at Takasaki Research Institute of Japanese Atomic Energy Agency (JAEA) was used to irradiate the samples with a dose rate of 467.7 Gy/h to doses up to about 10 k Gy.This k-value would be much more realistic than previous value in the sense that the present value was obtained with using the natural barite extracted from a hydrothermal sulfide deposit which is actually used in dating while Toyoda .(2012) examined the barite crystal occurring on land.
3 where single saturating exponential curves were fitted to the dose responses for natural samples and exponential with linear functions (Duval, 2012) were for the synthetic sample.This value is 19% higher than the previously reported value of 0.043 ± 0.018 (Toyoda ., 2012).