When selecting 14w29 snapshots it will launch, but won't go further than the Mojang logo. It crashes instead. I've tested it on other iMacs with different OS versions and it seems to affect all macs
MC-62179
14w29a/b startup crash
Resolved
Incomplete
0
Incomplete without a crash report (
[minecraft|http://hopper.minecraft.net/help/finding-minecraft-data-folder]/crash-reports/crash-<DATE>-client.txt). Please attach it so that we can diagnose your issue.