the mistake is as much mine as anyone else - it was me that used the word in the first place, so apologies for the initial confusion. I had thought always that opaline was the one which gave the 'sunset' glow. However, I was wrong, and stand corrected, and my sincere thanks to Lustrousstone for her technical expertise and help. So, now I know, and just to show that I know, am going to bore you all with three pieces of 'opalescent'
glass, just to prove I can tell the difference (each in ordinary view, and then with a lighted backdrop). In the event it would appear that I do not have any 'opaline' at all, so must go out and try and find some