CC Ādi 7.126

nānā ratna-rāśi haya cintāmaṇi haite
tathāpiha maṇi rahe svarūpe avikṛte
Word for word: 
nānā — varieties; ratna-rāśi — valuable jewels; haya — become possible; cintāmaṇi — the touchstone; haite — from; tathāpiha — still, certainly; maṇi — the touchstone; rahe — remains; svarūpe — in its original form; avikṛte — without change.
Translation: 
“Although a touchstone produces many varieties of valuable jewels, it nevertheless remains the same. It does not change its original form.