Charak Samhita
अनम्लं च कषायं च कटु पाके शिलाजतु। नात्युष्णशीतं धातुभ्यश्चतुर्भ्यस्तस्यसम्भवः ॥४८॥
[Properties of Shilajatu rasayana] Shilajatu originates from four metals – gold, silver, copper and black iron and is slightly sour, astringent in taste, katu in vipaka and is moderate in veerya.
english translation
anamlaM ca kaSAyaM ca kaTu pAke zilAjatu। nAtyuSNazItaM dhAtubhyazcaturbhyastasyasambhavaH ॥48॥
hk transliteration by Sanscript