Wednesday, June 30, 2010

July 2010 Mineral of the Month


Howlite, a calcium borosilicate hydroxide (Ca2B5SiO9(OH)5), is a silicate mineral found in evaporate deposits. Howlite was discovered at Tick Canyon, California in 1868 by Henry How (1828-1879) He was a Canadian chemist, geologist, and mineralogist. In appearance, it is white with fine gray or black veins in an erratic, often web-like pattern, and is opaque with a sub-vitreous luster. Slabs of Howlite are often painted with scenes and designs that make artistic use of these veins. Its structure is monoclinic with a Mohs hardness of 3.5 and lacks regular cleavage. It is most often found in massive nodules that resemble a head of cauliflower and rarely in crystal form as tabular prisms.

Howlite is commonly used to make decorative objects such as small carvings or jewelry components. Because of its porous texture, Howlite can be easily dyed to imitate other minerals, especially turquoise because of the superficial similarity of the veining patterns. Howlite is also sold in its natural state, sometimes under the misleading trade names of "white turquoise" or "white buffalo turquoise", or the derived name "white buffalo stone". Sometimes Howlite fluoresces a blue, yellowish white or off white color under shortwave UV light and dissolves in hydrochloric acid solution without bubbling.