Agate is formed from microscopic crystal of quartz laid down in bands.  It is a very stable crystal.  Agates are grounding stones bringing about an emotional, physical, and intellectual balance.  They aid in centering and stabilising physical energy.  Agate has the power to harmonise yin and yang, the positive and negative forces that hold the universe in place.  A soothing and calming crystal, Agate works slowly but brings great strength.  Its multiple layers can bring hidden information to light.
This heart is just perfect for your desk, bedside table or your special place. I haven't seen many pieces like these. Just beautiful! The picture say more than I can. Weighs almost 800 grams
* Judy Hall "The Crystal Bible" 2009

Agate (Blue) Crystalised Heart large (almost 800 grams)