Chemical composition -- Hydrated calcium borosilicate.
Color -- White.
Optics -- R.I 1.58-1.60.
Durability -- Hardness 2-3.5.
Crystal structure -- Monoclinic. Usually found in massive nodules.
Specific Gravity -- 2.45-2.58.
Sources -- Howlite is abundant in California and also occurs in Nova Scotia. Unimpressive in its native state, howlite is frequently dyed blue and makes a convincing substitute for turquoise. Since it's available in fairly large sizes and is quite soft, it is often used in carvings.