Give honour where honour is due. The very first site I want to refer to is the English speaking site Mindat.org . This site is not only titanic, but also very serious and visual. There you will find all possible information on minerals, mineralogy and crystallography. It is on this site that I find the illustrations concerning crystallography.
The first French-speaking site is that of Patrick Voillot: PatrickVoillot.com . This site has a very nice free encyclopedia to refer to. Patrick is also the producer of 23 films on gemology, translated into 8 languages, and available for free on his Youtube channel . Personally, it was after watching his film “ the sapphires of Kashmir ” that my passion for gemology was born.
Another French-speaking reference site is that of Thierry Pradat: Gemmo.eu . Thierry is a gem trader who has an excellent business site: Gemplus . You can also find your reference stones there.
To go further
books (to come)
magazines (to come)