Almond tree - how to harvest

[dementedma]

We have an almond tree which has a large crop this year. They are like green marbles at the moment. Are they safe to eat and when/how do we harvest them?

I've only ever harvested them in Spain (used to live there) - there you wait until the green marble-like fruits start to split open, and you can see the shell of the nut hardened inside, they're ready mid August IIRC but obviously much hotter!.
They're good to eat if they're sweet almonds - if they're bitter (not good to eat) they taste horrific, you really wouldn't be able to swallow one, so just have a tentative nibble on a nut.