Maxixe — The Beryl Whose Blue Fades in Sunlight
Maxixe — The Beryl Whose Blue Fades in Sunlight
A radiation-induced blue, named for a Brazilian mine and notorious for its instability
Maxixe is a deep blue beryl whose colour is caused by radiation-induced colour centres rather than by the iron-related mechanism that gives stable aquamarine its blue. The name derives from the Maxixe mine in Minas Gerais, Brazil, where the variety was first described in 1917. Maxixe-type beryl is among the more notorious unstable colours in the gem world: in prolonged daylight or at moderate heat, the deep blue fades to pale blue, greenish, or colourless, depriving the stone of the property that made it interesting in the first place. For this reason, maxixe beryl has remained a collector curiosity rather than a viable commercial gem.
The two colour mechanisms in blue beryl
Aquamarine — the stable, commercially significant blue beryl — is coloured by ferrous iron (Fe2+) substituted into the beryl structure. The colour is intrinsic to the lattice and is stable against light and moderate heat. Maxixe blue is fundamentally different: it arises from radiation-induced colour centres, lattice defects produced when natural or artificial ionising radiation knocks electrons out of position and traps them in defect sites that absorb in a way that produces the observed blue. These colour centres are thermodynamically metastable and decay back toward the un-trapped state with time, light, and heat.
Two distinct centres are recognised: the original Maxixe centre described from the Brazilian material, and the Maxixe-II centre identified later in beryl from other localities. Both produce a similar deep blue and both are unstable. The two centres can be distinguished by their absorption spectra and by their fading kinetics, but for practical purposes the trade treats them together as maxixe-type beryl.
Natural versus irradiated material
The original Brazilian Maxixe-mine material is a rare natural occurrence in which the colour centres are produced by natural background radiation over geological time. Most blue beryl with maxixe-type colour reaching the market today is the product of artificial irradiation — typically gamma radiation from a Cobalt-60 source — applied to pale or colourless beryl rough that lacks the iron content needed for stable aquamarine blue. The treatment produces an attractive deep blue at modest cost, and the irradiated material has appeared periodically in trade as a low-priced substitute for aquamarine. The fading problem makes the substitution short-lived in any practical sense.
Identification
Maxixe-type beryl can be distinguished from aquamarine by its absorption spectrum: maxixe beryl shows a characteristic strong absorption band in the red region of the spectrum that aquamarine does not, observable with a hand spectroscope. Pleochroism is also distinctive: stable aquamarine shows blue parallel to the c-axis and colourless or near-colourless perpendicular, while maxixe blue tends to show the deeper blue perpendicular to the c-axis. Laboratory testing using UV-Vis spectroscopy confirms the identification reliably.
The fading test itself is diagnostic but obviously destructive of the property under examination. A controlled exposure to strong daylight for a few hours will perceptibly fade maxixe-type beryl while leaving aquamarine unchanged.
Trade significance
Maxixe-type beryl is not a commercial gem in the conventional sense. The fading makes it unsuitable for jewellery wear, and reputable retailers do not stock it as a product. It does appear in collector channels, where the unusual colour history and the gemmological interest can outweigh the practical limitations. The trade-disclosure question is real: irradiated unstable blue beryl that is sold without disclosure as aquamarine constitutes a clear breach of the AGTA, CIBJO, and GIA disclosure standards. Buyers shopping for blue beryl at unusually low prices should be cautious and should request a laboratory report when the price seems out of line with stable aquamarine equivalents.
The original Maxixe mine
The Maxixe mine itself, in the Itabira region of Minas Gerais, was a small operation that produced the original material described in the 1917 literature. Production from the type locality was limited and the material is rare in original form. Most modern maxixe-type beryl reaching the market is irradiated from other beryl localities and bears no relationship to the original Brazilian source beyond the colour-centre mechanism that gives the variety its name.