əbsˈɪdiən, æz ɐ nˈætʃɚɹəl ɡlˈæs mətˈɪɹiəl, ɪz pɪkjˈuːlɪɹ bɪkˈʌz wɛn ɪɾ ɪz ɛkspˈoʊzd tə wˈɔːɾɚ, ðə sˈɜːfɪs dɪvˈɛləps ɐ pˈætᵻnˌeɪɾᵻd lˈeɪɚɹ ʌv haɪdɹˈeɪɾᵻd pˈɜːlaɪt.
Obsidian, as a natural glass material, is peculiar because when it is exposed to water, the surface develops a patinated layer of hydrated perlite.