De or het gemmologie?

The correct Dutch article is:

de gemmologie

Rule Words ending in -logie: always de. See the rule
Meaning (Dutch) (mineralogie) wetenschap die edelstenen en half-edelstenen bestudeert

How to use gemmologie

the gemmologiede gemmologie
this gemmologiedeze gemmologie
that gemmologiedie gemmologie
our gemmologieonze gemmologie
your gemmologiejouw gemmologie
every gemmologieelke gemmologie
which gemmologie?welke gemmologie?
a big gemmologie / the big gemmologieeen grote gemmologie, de grote gemmologie

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).