Matsya Purana — The Cave-Sanctuary: Jewel-Lake
कर्णिकाश्च तथा तेषां जातरूपस्य पार्थिव तस्मिन्सरसि या भूमिर् न सा वज्रसमाकुला //
karṇikāśca tathā teṣāṃ jātarūpasya pārthiva tasminsarasi yā bhūmir na sā vajrasamākulā //
And their pericarps (karnikā), O king, are of gold as well. The ground within that lake is not strewn with vajra-like hard stones and is free from obstructive gravel.
This verse does not describe Pralaya; it focuses on an auspicious sacred landscape—golden lotus-centers and land free from obstructive stones—used as a marker of purity and suitability.
It guides a ruler/householder in discerning auspicious, practical terrain: stone-free, stable ground near a sacred waterbody is implied to support dharmic settlement, ritual life, and public works without physical impediments.
It aligns with Vastu principles of site-selection (bhū-parīkṣā): land that is not ‘vajra-samākulā’ (cluttered with hard stones/gravel) is preferred for building and for establishing ritual spaces near tīrthas and saras.