From the same as soreq in the original sense of piercing; hetchelling (or combing flax), i.e. (concretely) tow (by extension, linen cloth) -- fine.
see HEBREW soreq
H8305. sariq
[שָׂרִיק] adjective carded, combed, of flax; — feminine plural שְׂרִיקוֺת מִּשְׁתִּים Isaiah 19:9.
II. שׂרק (compare Late Hebrew סָרָק light red; הִשְׂרִיק Ecclus 50:7; Ecclus 43:9 margin shine brightly (of sun); Assyrian šar‡u, red blood; Arabic rise and shine (of sun), shew redness, become red (like blood); Sabean שרק rise (of sun), משרק East, שרקן epithet dei the shining SabDenkm18, 4 FellZMG iiv (1900), 253 f. compare HomChr 124).