Howlite
Chemical Formula	Ca2B5SiO9(OH)5
Species	Borates
Crystal System	Monoclinic
Mohs Scale	3-6
Specific Gravity	2.53-2.59
Color	White, colorless
Streak	white
Luster	Sub-Vitreous
Refractive Index	n = 1.583 - 1.586 n = 1.596 - 1.598 n = 1.600
Diaphaneity	Translucent
Cleavage	None
Fracture	Conchoidal, uneven
Crystal Habit：Massive to nodular, occurs as tabular prisms flattened parallel to
Geological Setting：In borate deposits.