Heliodor - Encyclopedia

Class : Silicates
Subclass : Cyclosilicates
Crystal system : Hexagonal
Chemistry : Be₃Al₂Si₆O₁₈
Rarity : Common

Heliodor is a yellow variety of beryl, highly sought after as a gemstone. It is a typical variety of pegmatites and sometimes pneumatolytic veins. Its name comes from the Greek hêlios (sun) and dôron (gift), evoking its yellow color and its transparency. Like beryl, heliodor almost always occurs in elongated hexagonal prismatic crystals, vertically striated or grooved, sometimes short or flattened, rarely terminated. Its yellow color results from the presence of traces of iron in its crystal structure, replacing aluminum.

Main photo : Heliodor from Volodarsk-Volynskii, Ukraine © Oleg Lopatkin

Heliodor from Sherlova Gora, Nerchinsky, Russia © Oleg Lopatkin

Heliodor from Padre Paraíso region, Minas Gerais, Brazil

Heliodor from Vénachat, Compreignac, Haute-Vienne, France © François Husson

3.12 ct faceted heliodor from Brazil

Heliodor in the World

Heliodor is known in superb crystals in several parts of the world. Pegmatites from Russia, for example, have provided extraordinary combinations of heliodor, smoky quartz and blue topaz (Nerchinsky and Urul'ga), and superb centimeter-sized crystals (Mursinsk). The largest crystals come from Fazenda du Funil (Minas Gerais, Brazil) where they reach 20 cm, and from Volodarsk-Volynskii (Ukraine) in superb 15 cm crystals. Malagasy pegmatites also gave magnificent samples, as well as those from Namibia (Spitzkop) and Miami (Zimbabwe), where gem crystals of 7 cm were extracted in the 1960's.

Heliodor in France

In France, heliodor is known in certain pegmatites of the Ambazac mountains (Chanteloube, Compreignac) in Limousin (Haute-Vienne).

Twinning

No twins known for this mineral species.

Fakes and treatments

Heliodor can be obtained by irradiation and by heating aquamarine. The treatment is currently undetectable. Heliodor has been reported from several localities in the regions of Tajikistan, Afghanistan and Pakistan, it is most likely that all of these specimens are low quality aquamarines that have been irradiated to turn them golden yellow. No confirmed and verified evidence of the presence of heliodor on the ground in these areas has yet been released.

Right photo : Potentially irradiated heliodor from Zelatoya Vada Mine, Tajikistan

Hardness : 2.5
Density : -
Fracture : Undeterminated
Streak : Yellow

TP : Translucent to transparent
RI : 1.573 to 1.605
Birefringence : 0.032
Optical character : Uniaxial -
Pleochroism : None
Fluorescence : Yellow-green

Solubility : -

Magnetism : NoneRadioactivity : Strong

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