Green Tree Agate 1 1/4" Skull

Green Tree Agate
A stone of inner peace
Releases pent up emotions
Increases optimism
Enhances rapport with living things
Instills a feeling of safety during challenging situations
Brings strength and perseverance 
Encourages a positive sense of self and self-esteem 
Has a deep connection with nature
Helps plants and flowers to grow and thrive
 
Crystal Skulls
Help connect with spirit guides, ancestors, spiritual teachers and ascended masters
Can provide protection and healing when worked with
Can connect with ancient knowledge, as they are record keepers
Assist with channeling guidance
Can be held during meditation
You can also use them as part of a crystal grid
They each have their own personality and when asked, will give you their name
This is just a snippet of information.  There are many good books and articles to provide more information