Note 2 — THE EMERALD.
Reading edition
Footnote 2:
(return)
A curious result happened to the elder Silliman when experimenting with a Peruvian emerald before the compound blowpipe. The reducing flame instantly melted it into a transparent green globule. Perhaps the intense heat of this all-powerful flame, which reduces even the diamond, recalled the colors which disappear at a lower temperature. But this could not be done if the color was due to organic matter, which is annihilated or modified beyond recall by combustion.