Howlite is a calcium borosilicate hydroxide mineral with the chemical formula Ca₂B₅SiO₉(OH)₅, belonging to the monoclinic crystal system. It is characterised by a white to pale grey body colour traversed by irregular grey to black veining that imparts a striking, marble-like or web-like surface pattern. With a Mohs hardness of only 3.5 and a notably porous microstructure, howlite occupies an unusual position in the gem trade: it is used in its natural state for decorative jewellery and carvings, yet it is perhaps more widely encountered as a dyed simulant for turquoise, lapis lazuli, and other more valuable materials. Its ready acceptance of dye, low cost, and widespread availability have made it one of the most commercially significant imitation stones in the modern gem market.

Discovery and Nomenclature

Howlite was first described scientifically in 1868 by the Canadian geologist and chemist Henry How, after whom the mineral is named. How identified the material from deposits in Windsor, Nova Scotia, where it occurred as large, irregular nodular masses within gypsum-bearing evaporite sequences. The formal mineralogical description was subsequently published and the species accepted into the mineralogical literature. The Nova Scotia locality remains historically significant, though it is no longer the primary commercial source.

Physical and Chemical Properties

Howlite's chemical composition — a hydrated calcium borosilicate hydroxide — places it within the borosilicate mineral group, a relatively uncommon grouping in gem mineralogy. Its key physical properties are as follows:

• Chemical formula: Ca₂B₅SiO₉(OH)₅
• Crystal system: Monoclinic
• Hardness: 3.5 (Mohs scale)
• Specific gravity: approximately 2.53–2.59
• Refractive index: approximately 1.583–1.608 (biaxial negative)
• Lustre: sub-vitreous to dull on natural surfaces; polished surfaces show a waxy to sub-vitreous lustre
• Cleavage: none observed in massive material; fracture is uneven to conchoidal
• Transparency: opaque in virtually all gem-quality material
• Colour: white to pale grey with grey, black, or occasionally brown veining

The mineral rarely forms well-developed crystals; when crystals do occur, they are tabular and typically small, making them of interest primarily to mineral collectors rather than the gem trade. The commercially significant material is almost exclusively massive and nodular, sometimes occurring in masses of considerable size — nodules weighing several kilograms have been documented from Californian deposits.

The porosity of howlite is a defining characteristic from a gemological standpoint. The fine network of micro-pores distributed throughout the material allows liquids, including dyes, to penetrate deeply and relatively uniformly, producing a stable, even coloration that can be difficult to distinguish from natural coloured stones without laboratory testing.

Principal Localities

The most commercially important howlite deposits are located in California, United States, particularly in Los Angeles and San Bernardino counties, where the mineral occurs in association with borate deposits — the same geological environment that hosts borax and other economically significant borates. The Tick Canyon area and localities in the Mojave Desert region have historically been productive. California material is typically fine-grained, white, and well-veined, making it particularly suitable for both natural use and dyeing.

Nova Scotia, Canada, represents the type locality and retains historical importance, though commercial production there has been limited in recent decades. Additional occurrences have been recorded in Newfoundland, Mexico, Turkey, Germany, and Russia, though none of these rival the Californian deposits in terms of gem-trade significance.

Howlite as a Natural Gem Material

In its undyed state, howlite possesses a quiet, restrained beauty. The white to cream ground colour, interrupted by sinuous grey or black veining, bears a resemblance to certain marbles and to white magnesite, with which it is frequently confused or conflated in the trade. Beads, cabochons, tumbled stones, and carved objects fashioned from natural white howlite have found a consistent market, particularly in the context of fashion jewellery and decorative objects where the marble-like patterning is valued for its own sake.

The low hardness imposes practical limitations: howlite is susceptible to scratching from everyday contact, and pieces set in rings or bracelets subject to abrasion will show surface wear relatively quickly. It is better suited to pendants, earrings, and beads where mechanical stress is lower. The material takes a reasonable polish, though the surface finish is never as brilliant as that achievable on harder gem species.

Carvings in howlite — particularly animal figurines, skulls, and decorative spheres — have become popular in the mineral and metaphysical markets, where the material is sometimes marketed under the name white buffalo stone or white turquoise, terms that, as discussed below, carry significant potential for consumer confusion.

Dyeing and Use as a Simulant

The most consequential aspect of howlite in the gem trade is its use as a dyed simulant for turquoise and, less commonly, for lapis lazuli, red coral, and other materials. The process is straightforward: howlite nodules or pre-cut pieces are immersed in a dye solution — typically a blue or blue-green dye for turquoise imitation, or a deep blue for lapis imitation — and the porous structure draws the colourant throughout the material. The resulting product can be visually convincing to the untrained eye, particularly when the natural grey veining of howlite mimics the matrix patterns characteristic of genuine turquoise.

Dyed howlite sold as turquoise has been documented in the gem trade under a variety of trade names, most notably buffalo turquoise and white buffalo turquoise. These designations are misleading and, in many jurisdictions, constitute misrepresentation when applied to dyed howlite. The Federal Trade Commission in the United States and equivalent consumer protection bodies in other countries have addressed the issue of misleading simulant nomenclature, and reputable gem laboratories including the GIA have documented the prevalence of dyed howlite in the turquoise market.

It should be noted that white buffalo turquoise is also a legitimate trade name applied to a genuine, naturally white turquoise variety mined at the White Buffalo mine in Nevada — a material that is indeed turquoise by composition but lacks the blue colour associated with the species. The overlap in terminology between this genuine material and dyed howlite creates persistent confusion in the marketplace, and buyers encountering either name should seek laboratory verification.

Dyed howlite imitating lapis lazuli is typically coloured with a deep blue dye and may have pyrite inclusions added artificially to further the resemblance, though this level of elaboration is less common. Red-dyed howlite has appeared as a coral simulant, and black-dyed material has occasionally been offered as jet or black onyx.

Identification and Separation from Simulants

Separating howlite from the materials it imitates, and identifying it correctly when encountered in undisclosed form, relies on a combination of gemological observations:

• Hardness: At 3.5 on the Mohs scale, howlite is softer than turquoise (5–6), lapis lazuli (5–6), and most other materials it imitates. A simple scratch test on an inconspicuous area can be informative, though destructive testing is not always appropriate.
• Specific gravity: Howlite's SG of approximately 2.53–2.59 is lower than that of genuine turquoise (2.60–2.90) and considerably lower than lapis lazuli (2.7–2.9), though the overlap with some turquoise values makes SG alone insufficient.
• Surface examination: Under magnification, the surface texture of howlite often appears granular or chalky, and the veining pattern, while superficially similar to turquoise matrix, tends to be more irregular and less mineralogically consistent than genuine turquoise matrix.
• Dye detection: Dyed howlite frequently shows dye concentration along surface cracks and in porous areas, visible under magnification as uneven colour distribution. A cotton swab moistened with acetone may lift surface dye in some cases, though deeply penetrated dyes may not respond to this test.
• Ultraviolet fluorescence: Natural howlite may show a pale yellowish or greenish fluorescence under long-wave ultraviolet light, a reaction not typically seen in genuine turquoise.
• Spectroscopic analysis: Infrared spectroscopy and Raman spectroscopy provide definitive identification, clearly distinguishing howlite from turquoise, lapis lazuli, and other simulants by their characteristic absorption spectra. These techniques are routinely employed by gem laboratories.

The GIA and other accredited laboratories routinely identify dyed howlite in submitted parcels, and their reports will clearly state the material as howlite with a notation of artificial colouring treatment. Consumers purchasing turquoise, lapis lazuli, or coral at lower price points are well advised to request laboratory documentation.

Confusion with Magnesite

Howlite is frequently confused with magnesite (magnesium carbonate, MgCO₃), another white, porous mineral with similar grey veining that is also widely dyed as a turquoise simulant. The two materials are distinct species with different chemical compositions and slightly different physical properties, but they are often conflated in the trade and in popular literature, sometimes sold interchangeably under the same misleading trade names. Magnesite has a slightly higher specific gravity (approximately 2.9–3.1 for pure material, though gem-quality massive material is often lower) and different infrared absorption characteristics. Both materials share the fundamental issue of being porous, low-hardness white minerals that readily accept dye and are commercially exploited as simulants.

Market Context and Trade Considerations

Howlite occupies a well-defined, if somewhat unglamorous, position in the gem market. As a natural material, it is inexpensive — beads and cabochons are available at wholesale prices that reflect its abundance and ease of processing. There is no meaningful investment market for howlite, and its value is essentially determined by craftsmanship and design rather than by the intrinsic worth of the material itself.

The more commercially significant dimension is the simulant trade. Dyed howlite is produced in very large quantities, primarily in China, and distributed globally through wholesale bead markets, fashion jewellery manufacturers, and online retail platforms. The material is sold both honestly — labelled as dyed howlite or howlite simulant — and dishonestly, as turquoise or under misleading trade names. The honest trade in dyed howlite is entirely legitimate; the material is attractive, affordable, and suitable for fashion jewellery when properly disclosed. The problem lies exclusively in misrepresentation.

For retailers and consumers, the practical guidance is straightforward: any turquoise-coloured material offered at prices significantly below market rates for genuine turquoise — particularly in bead form or in large quantities — warrants scrutiny. Genuine turquoise of good colour and quality commands substantial prices, and material offered at a fraction of those prices is almost certainly either dyed howlite, dyed magnesite, or a stabilised and heavily treated turquoise of low natural quality.

The metaphysical and crystal healing market represents a significant consumer base for howlite, where the material is marketed for its supposed calming properties and is sometimes assigned specific energetic attributes. This market is largely indifferent to gemological distinctions, and the same piece of material may be sold as white howlite, white buffalo stone, or blue howlite (when dyed) depending on the vendor's terminology. Gemologists and jewellery professionals should be aware of this parallel market and the nomenclature it employs.

Care and Handling

Howlite jewellery requires careful handling given the material's low hardness and porosity. The following precautions are appropriate:

• Avoid contact with harsh chemicals, including household cleaners, perfumes, and hairsprays, which may strip or alter dye in treated material and may damage the surface of natural howlite.
• Clean only with a soft, slightly damp cloth; ultrasonic and steam cleaners are contraindicated.
• Store separately from harder gem materials to prevent scratching.
• Prolonged exposure to direct sunlight may cause fading in dyed material.
• Avoid immersion in water for extended periods, as the porous structure may absorb moisture and, in dyed material, may allow dye migration.

Further Reading

• GIA — Turquoise Simulants and Identification
• GIA — Gems & Gemology (journal archive)
• International Gem Society — Howlite