Howlite

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Howlite
Howlite.jpg
General
Category Inoborates
Formula
(repeating unit)		Ca2B5SiO9(OH)5
IMA symbol How [1]
Strunz classification 6.CB.20
Dana classification25.3.5.1
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/c
Unit cell a = 12.82 Å, b = 9.351(1) Å
c = 8.608(2) Å; β = 104.84(2)°; Z = 4
Identification
ColorWhite, colorless
Crystal habit Massive to nodular, occurs as tabular prisms flattened parallel to [100]
Cleavage None
Fracture Conchoidal, uneven
Mohs scale hardness3.5
Luster Subvitreous, glimmering
Streak white
Diaphaneity Translucent
Specific gravity 2.53 – 2.59
Optical propertiesBiaxial (−), colorless (transmitted light)
Refractive index nα = 1.583 – 1.586 nβ = 1.596 – 1.598 nγ = 1.600
Birefringence δ = 0.017
2V angle 73°
References [2] [3] [4]

Howlite, a calcium borosilicate hydroxide (Ca 2 B 5 Si O 9(OH)5), is a borate mineral found in evaporite deposits. [5]

Contents

History

Howlite was discovered near Windsor, Nova Scotia, in 1868 by Henry How (1828–1879), a Canadian chemist, geologist, and mineralogist. [6] [7] How was alerted to the unknown mineral by miners in a gypsum quarry, who found it to be a nuisance. He called the new mineral silico-boro-calcite; it was given the name howlite by the American geologist James Dwight Dana shortly thereafter.

Geology

The most common form of howlite is irregular nodules, sometimes resembling cauliflower. Crystals of howlite are rare, having been found in only a couple localities worldwide. Crystals were first reported from Tick Canyon in the Sierra Pelona Mountains of California, [8] and later at Iona, Nova Scotia. Crystals reach a maximum size of about one centimeter. [2] The nodules are white with fine grey or black veins in an erratic, often web-like pattern, opaque with a sub-vitreous luster. The crystals at Iona are colorless, white or brown and are often translucent or transparent.

Its structure is monoclinic with a Mohs hardness of 3.5 and lacks regular cleavage. Crystals are prismatic and flattened on {100}. [8] The crystals from Tick Canyon are elongated along the 010 axis, while those from Iona are elongated along the 001 axis.

Jewelry

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 trade names of "white turquoise" or "white buffalo turquoise," or the derived name "white buffalo stone" and is used to produce jewelry similar to how turquoise is used. Varieties of the unrelated gemstone turquoise which are white instead of the typical blue or green color have been mined in the US States of Arizona and Nevada, and are also marketed as "white buffalo turquoise". Most of the white varieties of turquoise are chalk-like with a Mohs hardness of 1, and are not as hard or durable as howlite, and subsequently require stabilization in order to be used in jewelry, which has resulted in howlite being more popular for use in jewelry than the artificially stabilized white forms of the mineral turquoise. [9]

See also

Related Research Articles

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<span class="mw-page-title-main">Kernite</span>

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2B
4O
6(OH)
2·3H
2O. It is a colorless to white mineral crystallizing in the monoclinic crystal system typically occurring as prismatic to acicular crystals or granular masses. It is relatively soft with Mohs hardness of 2.5 to 3 and light with a specific gravity of 1.91. It exhibits perfect cleavage and a brittle fracture.

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2 – xAl
x(H
2Si
2O
5)(OH)
4⋅nH
2O (x < 1) or (Cu, Al)
2H
2Si
2O
5(OH)
4⋅nH
2O).

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<span class="mw-page-title-main">Seamanite</span>

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<span class="mw-page-title-main">Studenitsite</span>

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<span class="mw-page-title-main">Bayleyite</span> Uranium carbonate mineral

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<span class="mw-page-title-main">Brianyoungite</span>

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<span class="mw-page-title-main">Faustite</span>

The IMA-approved mineral faustite is a member of the triclinic turquoise group of hydrous phosphates with the chemical composition ZnAl6(PO4)4(OH)8·4H2O. It is named after the American mineralogist and petrologist Dr. George Tobias Faust, who workes with the U.S. Geological Survey (USGS).

Henry How was a British-Canadian chemist, geologist and mineralogist.

Tuzlaite is a borate mineral, associated with halides, named after the Tuzla salt mines in Bosnia and Hercegovina. A multitude of rare evaporate minerals have been discovered there, it being the only major evaporate deposit in the Balkans. This mineral has been approved as tuzlaite by the International Commission on New Minerals and Mineral Names.

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. 1 2 "Handbook of Mineralogy" (PDF).
  3. ↑ "Howlite: Howlite mineral information and data". www.mindat.org.
  4. ↑ Barthelmy, Dave. "Howlite Mineral Data". webmineral.com.
  5. ↑ Howlite at Mineral Galleries
  6. ↑ H. How, "Contributions to the Mineralogy of Nova Scotia, Pt. III, Borates and Other Minerals in Anhydrite and Gypsum," Philosophical Magazine, January 1868
  7. ↑ Ramik, Robert A., "Lost and Found: one of Canada's earliest type mineral localities", The 32nd Rochester Mineralogical Symposium, Program and abstracts, Rochester, New York, April 14–17, 2005.
  8. 1 2 Murdoch, J., "Crystallography and X-ray measurement of howlite from California", American Mineralogist, 42, 521–524, 1957.
  9. ↑ "White Turquoise Facts – Durango Silver Company". www.durangosilver.com.

Bibliography

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