Mahabharata 12.205.6

लोहयुक्तं यथा हेम विपक्वं न विराजतेतथापक्वकषायाख्यं विज्ञानं न प्रकाशते

lohayuktaṃ yathā hema vipakvaṃ na virājatetathāpakvakaṣāyākhyaṃ vijñānaṃ na prakāśate

Our plain-language meaning of this verse is waiting for scholar review.