This is a small slab piece of Blue Aventurine. It measures approx. 50 x 34 mm: thickness is 6 mm: weight is 14 grams. This piece is from India.
 
Aventurine is a form of Quartz that has Mica inclusions to give it that glittery/shimmering appearance. Blue Aventurine gets is color from inclusions of Dumortierite. AKA Stone of Opportunity. MOHS is 6.5-7 and found in China, India, Brazil.