Srimad-Bhagavatam: Canto 8 - Chapter 1 - Verse 35

Sanskrit:

निपतन्स गिरिस्तत्र बहूनमरदानवान् ।चूर्णयामास महता भारेण कनकाचल: ॥ ३५ ॥

ITRANS:

nipatan sa giris tatrabahūn amara-dānavāncūrṇayām āsa mahatābhāreṇa kanakācalaḥ

Translation:

The mountain known as Mandara, which was extremely heavy, being made of gold, fell and smashed many demigods and demons.

Purport:

By constitution, gold is heavier than stone. Since Mandara Mountain was made of gold and was therefore heavier than stone, the demigods and demons could not properly carry it to the Ocean of Milk.