Howlite is a borate mineral originally referred to by its discoverer, Canadian professor Henry How, as silicoborocalcite. Howlite usually occurs in massive form and has a marble-like appearance. It lends itself well to carving, as well as dying due to its white color and is often dyed to resemble turquoise.
Chemical composition: Ca2B5SiO9(OH)5
Hardness: In massive form 3.5; in crystal form 6.5