Invited by Buffon to Paris, Faujas ceased his legal work and was appointed assistant naturalist to the natural history museum by Louis XVI.

In his capacity of commissioner for mines Faujas travelled to most European countries where he closely observed the natural environment and the rock formations.

He however was determined to visit Staffa and he set out with the American polymath William Thornton and the Italian balloonist Count Andreani.

The island was visited earlier in 1772 by Sir Joseph Banks, who remarked that the stone was a coarse kind of basalt, very much resembling the Giant's Causeway in Ireland (as noted in Pennant's Tour in Scotland and Voyage to the Hebrides).

Faujas' Voyage en Angleterre, en Écosse et aux Îles Hébrides (1797) contains anecdotes about Sir Joseph Banks, William and Caroline Herschel and Dr. John Whitehurst, including an amusing account of The Dinner of an Academic Club (the Royal Society).

Faujas was appointed the first professor of geology at the Jardin des Plantes in 1793, a post he held until he was nearly eighty years of age.