On 2015-12-16, Stephen Wolstenholme wrote:

There are avocado stones in my compost but I've never noticed how long
they have survived.

Have you ever tried eating the skin? When I was about 12 I was at a
posh dinner. The salad included chopped up avocado. I didn't know I
was supposed to cut or bite the soft part off the skin. I just chewed
it until it went down the hatch!

It sounds quite bizarre --- to me, anyway --- that someone would chop
up an avocado with the skin still on to put in a salad.

A quick Google finds many different sorts of avocado. They don't all
have tough skins.

Except in one of those cases.