These reactions are somewhat modified by the presence of noncarbonate 

 constituents or the physical characters of the specimen. 



Finely disseminated anhydrite, clays, and other inert substances retard the 

 acid reaction sufficiently to cause a limestone to react like dolomite or dolomitic 

 limestone. However, there are at least two ways in which to distinguish them. 

 The reaction of dolomite is very slow at first, but becomes more vigorous after 

 a few minutes or seconds in the acid. Impure limestone will effervesce strongly 

 at first, but the reaction progressively lessens. A pure dolomite is entirely sol- 

 uble; an impure limestone leaves an insoluble residue when acid reaction has 

 ceased. 



Limestone Dolomitic Calcific Dolomite 



Limestone Dolomite 



B 



Figure 3-4. Acid tests of carbonate rocks. A — Glass furniture leg coaster used for acid. 

 B — Characteristic reactions of limestone and dolomite. 



Very porous and permeable dolomite may react like a limestone because 

 of the greater surface area exposed to the action of the acid and the greater 

 buoyancy due to pore spaces. Some allowance must be made for such rocks 

 in appraising acid reactions. One should attempt to select less porous chips from 

 the sample for testing. 



Concentrated acid has higher viscosity and specific gravity than dilute 

 acid. The high viscosity permits greater accumulation of the C0 2 beads in 

 the acid above the specimen, and greater buoyancy is provided by the higher 

 specific gravity (and viscosity). To safeguard against misinterpretation, one 

 should use only acid diluted as specified earlier. 



Carbonate reaction is much more vigorous in warm acid than in cold. 

 Always make limestone-dolomite determinations in cold acid. 



Finely divided dolomite reacts like a limestone. This fact should be kept 

 in mind when one is examining finely ground cable-tool samples. Pulverized 

 dolomite on the surfaces of the chips will give an initial reaction similar to 

 limestone, but the reaction will slow down when the fine material has gone into 



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