Dear Venus,

If the limestone is not hard and compacted, you can try to use boiling water and adding hydrogen pyroxide with continuous stirrer for at least 72 hours (best for chalky and marly limestone). This method lead to get better and clean tests usually. If they are still coagulate, you can add, but be careful, very very little amount (one drop or two) of diluted sodium hydroxide (the later dissolved calcareous tests and etching siliceous tests).

Good Luck

A mixture of hydrogen peroxide and ammonia will do good for soaking and boiling marly and less jndurated limestone. For very hard compact limestone, I think several things sections will be better.

Thank you all

First of all, you have to crack the rock into small chunks then put it in a 1000ml beaker, add about 10 grams of sodium bicarbonate and boil for about one hour. Be careful, you have to try in a small piece to adjust the amount and duration of boiling.

Hello Dear Venous

In Reolid & Herrero (2004) paper: Article Evaluation of methods for retrieving foraminifera from indur...

There are 2 methods: First

Amine-O Method The 300g processed sub-sample was reduced to 279.51g. The weight residues in the different sieves are given in text-figure 1-A. The complete or partial picking of the fractions yielded a total of 1002 specimens. The foraminifera/gram ratio increases towards the finer fraction and varies from 1.03 in the 1000-500m sieve to 1268.19 in the 125-60m one.

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Second

Acetic acid Method The acetic acid method reduced 300.1g of the spongiolithic limestone sub-sample to 237.99g of total residue, with the >1000m fraction accounting for 210.09g (see text-fig. 1-A). A total of 3680 specimens were retrieved in the complete or partial picking of the sieved fractions. The foraminifera/gram ratio shows an increase from the coarser fractions to the fine-grained ones.

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At the end: in hard limestone thin-section method more common. For example "Orbitolinds family larger foraminifera" are better identified in thin-section.

I hope it cloud be helpfull.

regards.

Dear sir, try this method also

I have had good results with formic acid, but this method may not work well unless your fossils have been replaced with silica

Try using a sonic water bath (ultrasound) for a brief time to release the fossils of the matrix debris. I have had success with this method but....some of the fossils may also become damaged. Remember HSE though

Try to make some Thin Section.