Heliodor is Greek for 'gift or present from the sun'. The gemstone is a yellow-green coloured variety of the beryl species. The yellow component may vary from a pale yellow to a deep golden yellow.
Some references describe heliodor as 'golden beryl' and in others as 'all colours of yellow beryl'. When heliodor was first introduced as a separate variety of beryl it was not fully accepted. That may be the reason why different colour descriptions are sometimes given by different gem suppliers.
See varieties of Beryl.
Source locations for Heliodor include: Brazil, Madagascar and Namibia.
Pale heliodor may be irradiated to improve the colour.