"the kroke of the greek is related to the sanskrit sarkara which also mean pebble"

From the Apte Sanskrit Dictionary @
http:// http://aa2411s.aa.tufs.ac.jp/~tjun/sktdic/ :

The sanskrit word 'sharkaraa' (though the phonetic symbols used on the site make it 'zarkaraa') also means the following, all in keeping with the "gritty quality" you mentioned Helen...

"1. candied suger;

2. a pebble;

3. gravelly mould;

4. soil abounding in stony fragments;

5. a piece;

6. a potsherd;

7. any hard particle as in <&Jalazarkaraa> a nodule of water;

8. the disease called gravel;

9. golden earth"

What in the world are 7 and 8???