Keilim12: 7
[ז] דִּינָר שֶׁנִּפְסַל, וְהִתְקִינוֹ לִתְלוֹתוֹ בְּצַוַּאר קְטַנָּה — טָמֵא. וְכֵן סֶלַע שֶׁנִּפְסְלָה, וְהִתְקִינָהּ לִהְיוֹת שׁוֹקֵל בָּהּ — טְמֵאָה. עַד כַּמָּה תִּפָּסֵל וִיהֵא רַשַּׁאי לְקַיְּימָהּ? עַד שְׁנֵי דִינָרִין; פָּחוּת מִכָּאן — יָקוֹץ.
A dinar that became disqualified and one prepared it in order to hang it around a girl’s neck, is tamei. And likewise, a sela that became disqualified, and one prepared it in order to weigh with it, is tamei. To what degree may [a sela] become disqualified and it will [still] be permitted to keep it? Up to two dinars. Less than that, he must cut up [the coin].