Puṣṭa Kṛṣṇa: Śrīla Prabhupāda, did the people, in order to get valuable minerals and gold and things like that, did they mine underneath the ground?
Prabhupāda: No. There was no need of coal. And the jewelries and stones were received from the sea—pearls; valuable stones from the hills.
Puṣṭa Kṛṣṇa: So they didn't dig deep holes underneath the ground?
Prabhupāda: No. There was no need. The richest persons' property were ivory, gold, marble, valuable jewels, pearls, silk. This was luxury, not plastic. Now they have advanced, they have got plastic; no gold, no silver. Paper money and plastic utensils. This is advancement.
Brahmānanda: Do we consider ivory as something pure or impure?
Prabhupāda: No, pure.
Brahmānanda: It is pure.
Prabhupāda: Ivory, yes. There is a current proverb, "Dead elephant, one lakh rupees." Mara hati lakṣa na:(?) "Elephant, alive or dead, one lakh of rupees," on account of ivory. When the elephant is dead, it is put into a hole and covered. And after sometimes you find all the ivory. The bones and the teeth are very, very valuable. Formerly big, big kings, they used to manufacture their furniture of ivory and gold and silk pad. This is luxury. And the rooms bedecked with jewel. No electricity, no lamp. This is description of Kṛṣṇa's sixteen thousand palace. Who has got now? Sixteen thousand wives and sixteen thousand palace of marble and furniture ivory and gold. Where is there now? Therefore Kṛṣṇa is the richest. Aiśvaryasya samāgrasya (Viṣṇu Purāṇa 6.5.47).