The River of the Śālagrāmas
The Gandakī river (also called Kali-Gandak or Nārāyaṇī in different stretches) originates in Nepal and flows through the Himalayas before joining the Gaṅgā in Bihar. The specific stretch of the Gandakī that produces śālagrāma stones is near the Muktinath temple in Nepal — a region called Damodara-kunda or Śālagrāma-kṣetra.
The River as Devī
The Gandakī is personified as Gandakī Devī — a goddess who holds the śālagrāma stones as children within her body. The river's water itself is considered sacred — pilgrims collect it along with śālagrāma stones.
The mythological origin: the Gandakī was a devotee of Viṣṇu who asked to bear the Lord in her womb — and was granted the boon that the śālagrāma stones in her bed would be his eternal presence.
Collection and Reverence
Śālagrāma collection (śālagrāma-kṣetra-yātrā) at the Muktinath area in Nepal is one of the Vaishnava pilgrimages undertaken with great reverence. Pilgrims do not simply "take" a stone but receive it with prayers and reverence, understanding that they are receiving the Lord himself in portable form.
The worm (vajra-kīṭa) that naturally carves the spiral groove in the śālagrāma stone is considered sacred — it is the Lord's own instrument of self-manifestation.