Pictured is an example, (stones sold individually) shapes and color may vary somewhat
Elestial crystals are also known as jacare or skeletal quartz. The name skeletal is due to the skeletal appearance of marking which are common on elestials.
In the case of an elestial, the crystal grows so fast that the layers trap things within them. Other crystals do this also, such as crystals with phantoms in them. But elestials often trap air or things such as acids within them as they grow. These acids then eat away at the inside of the crystal producing the classic skeletal appearance that elestials often have
 
Small 15mm
Medium 20mm
Large 25mm