▁had ▁found ▁a ▁piece ▁of ▁the ▁Moon ' s ▁prim ord ial ▁cr ust , ▁but ▁later ▁analysis ▁initially ▁showed ▁that ▁the ▁rock ▁was ▁only ▁ 4 . 1 ▁ ± ▁ 0 . 1 ▁billion ▁years ▁old , ▁which ▁is ▁younger ▁than ▁the ▁Moon ▁itself , ▁and ▁was ▁formed ▁after ▁the ▁Moon ' s ▁cr ust ▁solid ified . ▁It ▁is ▁still ▁an ▁extremely ▁old ▁sample , ▁formed ▁during ▁the ▁Pre - N ect arian ▁period ▁of ▁the ▁Moon ' s ▁history . ▁D ating ▁of ▁py ro x enes ▁from ▁other ▁lun ar ▁an orth os ite ▁samples ▁gave ▁a ▁sam arium – ne od ym ium ▁age ▁of ▁ ▁cry st all ization ▁of ▁ 4 . 4 6 ▁billion ▁years . ▁ ▁See ▁also ▁ ▁Apol lo ▁ 1 5 ▁operations ▁on ▁the ▁L un ar ▁surface ▁ ▁Had ley – Ap enn ine ▁ ▁An orth os ite ▁ ▁References ▁ ▁External ▁links ▁L un ar ▁and ▁Planet ary ▁Institute ▁- ▁Apol lo ▁ 1 5 ▁NASA ▁- ▁Apol lo ▁ 1 5 ▁Disc over ing ▁the ▁Gen esis ▁Rock ▁ ▁( From ▁the ▁Apol lo ▁L un ar ▁Sur face ▁Journal , ▁scroll ▁down ▁to ▁ 1 4 5 : 4 1 : 4 8 .) ▁A str onaut ▁Scott ▁exam ines ▁the ▁Gen esis ▁rock . ▁ ▁( image ) ▁ ▁An ▁over view ▁of ▁the ▁samples ▁collected ▁by ▁Apol lo ▁ 1 5 . ▁ ▁( The ▁Gen esis ▁Rock ▁is ▁sample ▁# 1 5