Determining if a mushroom is edible ?

[Externet]

Greetings. 

Is there a method with science instead of the tales of experts, to analyze if a mushroom will put me in a casket or not ?

My backyard has since a couple of days, shiny gold color 15cm. mushrooms on sunlight, silver color when overcast.  How to preserve them alive or ensure their propagation ?  The smell is just like fresh champignons.  Went to take pictures a moment ago, a visitor intruded.  Color today shows as more whitish.  Would a close-up image of some part help identifying ?

Adding pictures...

[iNow]

I’m certain with sufficient chemistry knowledge and equipment one could identify toxins in various fungi found while foraging, but mostly this is an issue of education and apprenticeship under experts. 

Pictures for identification should include cap, stalk, gills, and surroundings in the field coupled with location and time of year. 

All mushrooms are edible, but some only once.