Obsidian is an excellent grounding, protection and transmutation stone.  Blue Obsidian stimulates and enhances all forms of communication and lingual skills, when used at the throat chakra. It aids divination and psychic development pursuits.
Rare in its natural form this is a man made crystal. 

The crystal pictured is the one you receive 

83.9g

48.4mm x 39.8mm x 28.1mm

All measurements are approximate