Howlite is an interesting mineral that is sometimes used as a gemstone, though often masquerading as a better-known and more valuable gem type. In fact it is fair to say that howlite is more famous for imitating other minerals than it is in its own right.
By chemical composition, howlite is calcium borosilicate hydroxide. It was first discovered at Tick Canyon in Southern California in 1868. It was named after Henry How (1828-1879), a Canadian mineralogist who first described it.
Howlite is typically white or grayish-white with fine grey, black or brown veins, often in a web-like pattern. It is opaque with a sub-vitreous luster sometimes described as porcelaneous. Its crystal structure is monoclinic and it has a hardness of 3.5 on the Mohs scale. Howlite has a refractive index of 1.583 to 1.600 and a specific gravity of 2.53 to 2.59. It has no cleavage. It is usually found in borax deposits in the desert clays of California.
Since howlite is fairly porous, it can be easily dyed to imitate other minerals. Due to the distinctive veining, howlite dyed a blue color makes a fairly convincing turquoise simulant. However, howlite is a much softer stone than turquoise (the hardness of turquoise is 5 to 6, wheras howlite's is only 3.5). Therefore, it can be identified from such inauthentic turquoise. Howlite has also been dyed deep-blue to simulate lapis lazuli, or red to imitate coral.
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".
Howlite is often carved to produce decorative objects. It is a fairly inexpensive material and large nodules resembling cauliflower heads have been found in California in pieces as large as 50 kilograms. Though howlite has also been found in Nova Scotia in Canada, most of the material on the market comes from sites in Los Angeles and San Bernardino counties in California.
- Prima Pubblicazione: February-03-2010
- Ultima modifica: January-23-2019
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