borates
Howlite
Ca2SiB5O9(OH)5
- Also known as
- white turquoisewhite buffalo stoneturquenite
- Crystal system
- monoclinic
- Hardness
- 3.5 on the Mohs scale
- Lustre
- dull
- Colour
- White with grey or black veining
- Where it forms
- In evaporite deposits associated with borate mining, as nodules.
- Chiefly from
- Nova Scotia, CanadaCalifornia, United StatesTurkey
Why it is that colour
Essentially white. Its veining resembles turquoise matrix, and that resemblance is the entire reason it is commercially significant.
Safety
Safe to handle. It is soft and porous, and the dyes used on it are not always well fixed — dyed howlite can transfer colour onto skin and fabric.
Where it comes from
Common and very cheap. It is the single most widely used substitute in the stone trade: porous, white, and it takes dye beautifully.
Historical use
A minor borate mineral of no economic importance in its own right.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Described in 1868 and named after the Canadian geologist Henry How. It has no traditional attribution of its own, and much of what circulates about it belongs properly to turquoise, whose place on the shelf it has taken.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
Howlite is the workhorse of stone imitation, and it is worth knowing by name because so much of what is sold as something else is this.
It is white, soft, porous and veined, and it soaks up dye. Dyed blue it becomes turquoise; dyed deep blue with gold flecks added it becomes lapis; dyed red it becomes coral; dyed green it becomes malachite. Undyed it is sold as white turquoise or white buffalo stone, neither of which is turquoise.
The test is straightforward. Howlite is hardness 3.5 and will scratch with a steel pin where turquoise at 5 to 6 will not, and dyed material usually shows colour concentrated in the veins and paler in the body — the reverse of natural turquoise, where the matrix veining is darker and the body is coloured throughout.
Identity checked against IMA-CNMNC master list, June 2025.