Nice cabinet sized specimen, consisting of a phlogopite crystal in a calcitic marble matrix, from the Koksha Valley, Badakhshan Province, Afghanistan.
Under shortwave UV, the phlogopite fluoresces bright yellow, and the calcite fluoresces weak red. Unlike many Afghan phlogopites, this one also reacts to midwave and longwave UV; the midwave response of the phlogopite shifts to a butterscotch color, and the calcite fluoresces bright red. Under longwave, the phlogopite fluoresces a nice reddish orange, and the calcite barely reacts.
Midwave UV produces the best response; but the orange longwave response of the phlogopite is very nice, which makes me think the specimen is at its best with midwave and longwave combined. I will eventually edit this post and add a picture of the specimen under MW+ LW. Since midwave UV produces the best response imho, it is shown first in the pictures below. Then the specimen is shown respectively under shortwave and longwave UV and lastly, in visible light.
Size: 6,3 cm X 4,2 cm X 3,8 cm
Midwave UV (310 nm UVB LED)
Specimen in visible light.