I also collect American Brilliant Cut Glass, {ABCG} and one of the tests we use to authenticate old glass {1875-1910} is the blacklight fluorescent test. I just tested and got a greenish hue that indicates manganese in the glass, dating it to that time period. After 1915, this isn't present and no green shows.
Here is the "test" from a ABCG publication:
["The most promising test for detecting counterfeit ware is use of a long-wave, 15 watt Blacklight-Blue Fluorescent Bulb in a dark room. Due to addition of manganese in old glass ingredients to neutralize iron (found in the sand), which caused a greenish cast to the blank, the glass fluoresces a soft yellow-green color, while modern glass glows pink or slightly purple. "]
I also computed the SPECIFIC GRAVITY on the weight, and came up with 2.75-2.85 range. I need to invest in a more accurate calibrated beaker I guess now that I know to test for SG as well.