There are two basic answers:
Opalescent glass is intentionally chemically formulated to achieve the opalescent effect. The chemical approaches to this were varied over time. Various aluminum compounds were normal as were some flourides.
The "effect" is caused by visual perception of the diverse optical frequencies that are close to the visual wavelength perception of the human eye.
Go in a Rock & Mineral gift shop and watch the parade of people that come in looking for various crystals to heal specific ailments, disease and pains. Its not just one or two people.
(Unfortunately, I have chosen to remove this content due to unchecked behavior by others on this board. Moderators may humor it because it comes from their "friend", but I will not. My apologies to those who will not benefit from it in the future.)
My opinion as a long-term handmade collector and as a person who has cane-cut experience in the studio: ........................
(Unfortunately, I have chosen to remove this content due to unchecked behaviors by others on this board. I will not insult or attack others and I expect the same from them. My apologies to those who will not benefit from it in the future.)
If you don't approve of members attacking other members - you might mention it to the moderators.
(Unfortunately, I have chosen to remove this content due to unchecked behaviors by others on this board. My apologies to those who will not benefit from it in the future.)