सर्वं च तिक्तकटुकं नात्युष्णं कटु पाकतः । छेदनं च विशेषेण लौहं तत्र प्रशस्यते ॥ १३१ ॥
All (varieties of it) are bitter, pungent, not very hot in potency, pungent at the end of digestion and especially possess the property of chedana (excision), among these, that coming out from iron is best.
गोमूत्रगन्धि कृष्णं गुग्गुल्वाभं विशर्करं मृत्स्नम् । स्निग्धमनम्लकषायं मृदु गुरु च शिलाजतु श्रेष्ठम् ॥ १३२ ॥
Smell like that of cow urine, black color, resembling guggulu – Commiphora mukul (in consistence), viśarkaraṃ – devoid of stones, softness, unctuousness, non-sour, non-astringent, soft and heavy are the properties of a good shilajatu. Purification of Shilajatu
It should be washed first with only water and dried and then soaked in the decoction of herbs suitable to the disease and the diseased and dried, collected and then kept in an iron vessel.
One part of asphaltum (Shilajatu) should be boiled in eight times its quantity of water mixed with the appropriate processing drugs. When the decoction is reduced to one-eighth, filtered, and still warm, asphaltum is added into it.
When it absorbs the liquid completely and dries up, it should be added to fresh decoction again. In this manner, it should be impregnated (given bhavana) with its respective decoctions seven times.