nipatan sa giris tatra
bahūn amara-dānavān
cūrṇayām āsa mahatā
bhāreṇa kanakācalaḥ
nipatan - falling down; saḥ - that; giriḥ - mountain; tatra - there; bahūn - many; amara-dānavān - demigods and demons; cūrṇayām āsa - were smashed; mahatā - by great; bhāreṇa - weight; kanaka-acalaḥ - the golden mountain known as Mandara.
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.