Subject: Is there a way to determine/test if something is silica gel?

recently i came across a museum specimen placed inside a box with these
small clear-yellowish beads.  at first i thought they were just some 
polymer bead that allowed the specimen to sit well with equal pressure on 
all sides.
someone else said that the beads are probably silica gel.  is there any 
test i can do to determine if the beads are silica gel?  also they said to 
throw them out because since they are yellow they aren't "good" anymore?  
Is this correct or can they be subjected to high heat and be "revived" to 
be used as a dessicant again?  Are they reactive towards other materials?  
I have noticed that silica gel is usually in bags or contained and kept 
seperate from other materials.

Re: Is there a way to determine/test if something is silica gel?