Tumblestone - Howlite, White (Natural) A single tumblestone measuring approximately 15mm - 25mm in size. £1.00 Quantity: at £1.00 each Add To Basket 0 in your basket View Basket Checkout Calming stone. It relieves insomnia and balances calcium levels within the body and aids teeth, bones and tissues. it teaches patience and helps to eliminate rage and uncontrolled anger calming turbulent emotions. Good for meditation.