Monazite crystals from a 50 m wide quartz vein in Montgomery County, North Carolina show the alexandrite effect. The crystals are reddish-orange under incandescent light, yellow-orange in daylight, and light green under fluorescent light. The colors are due to narrow absorption bands from Nd3+ at about 800, 745, 580, 525, and 515 nm, and an absorption edge beyond ≃480 nm. The monazite is chemically unusual in containing virtually no Th, U, or iron-group elements, which can cause deep colors that mask the pastel rare earth-produced colors. The alexandrite effect in this monazite differs from that in previously described substances in being due to several narrow absorption bands rather than a small number of broad bands.
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