Notable Isotopes 
24Mg [12 neutrons]
Abundance: 78.99%
Stable with 12 neutrons
25Mg [13 neutrons]Abundance: 10%
Stable with 13 neutrons
26Mg [14 neutrons]Abundance: 11.01%
Stable with 14 neutrons
| Large enrichments of stable 26Mg have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite meteorites. The anomalous abundance of 26Mg is attributed to the decay of its parent 26Al in the inclusions. |
| Therefore, the meteorite must have formed in the solar nebula before the 26Al had decayed. Hence, these fragments are among the oldest objects in the solar system and have preserved information about its early history. |