Pascal Garnier was the son of Jules Garnier*. He was educated at the Ecole Centrale, Paris, and qualified as an engineer. During his short life he undertook three journeys to the Southern Hemisphere. The first of these brought him to the Transvaal, where he and his father arrived in February 1895 to study the gold mines and diamond deposits of the territory. Pascal worked in Klerksdorp during March and April 1895 and then returned to Johannesburg. Jules had instructed him to make observations in the gold mines of the Witwatersrand to corroborate his hypothesis that mud deposits played a role in the formation of both diamondiferous and auriferous strata. Pascal found that thin carbon layers were associated with some gold-bearing reefs on the East and Central Rand and at Klerksdorp, and that both the carbon layers and the reefs in their vicinity were very rich in gold. This important finding was reported to the French Geographical Society in June 1895 and was presumably published under Jules Garnier's name in "Etude de la Formation Aurifere du Witwatersrand" in Comptes Rendus des Seances de la Societe de Geographie Commerciale (1895, pp. 277-279). During August 1895 Pascal visited Lydenburg. In November he left the Transvaal for Mozambique and from there returned to France. The next year father and son published a paper on "L'or et le diamant au Transvaal et au Cap" in the Memoirs of the (French) society of civil engineers.
Garnier's second journey took him to New Zealand to study its mines on behalf of the Franch Society of Civil Engineers. He arrived in Auckland in August 1896. After investigating three gold mining districts he left the country in September 1897 and reported his findings to the society in February the next year. Soon thereafter he left on his third journey, this time to Western Australia, where he was joined for some time by his father. However, he died there at the young age of 26 years. Their report on their investigations, with Pascal as co-author, was published in France in 1900.