Distinguishing between howlite and turquoise presents a common challenge for buyers, jewelers, and collectors alike. Both stones are popular in jewelry and decorative items, often appearing with similar blue-green hues and distinctive veining. However, their similarities are primarily superficial, especially when howlite is dyed to mimic turquoise. Understanding the fundamental differences in their physical, chemical, and geological properties is crucial for accurate identification, ensuring you acquire the genuine article or understand the material you are working with.
Key Visual Distinctions
While dyed howlite can closely resemble turquoise, careful observation of natural characteristics provides the first line of defense in identification.
Color and Hue
Natural howlite is typically opaque white or off-white, sometimes light gray, with characteristic dark gray, brown, or black veining. This veining often forms a spiderweb-like pattern. When dyed, howlite can achieve a wide spectrum of blue-green shades, but the underlying white base might still be subtly visible at points of wear or damage.
Turquoise, in its natural state, exhibits a distinct range of blue to green colors. The most prized specimens feature a vibrant sky-blue, often referred to as "robin's egg blue." Greenish hues are common and result from iron impurities, while blue shades come from copper. The color of natural turquoise is generally more saturated and complex than dyed howlite, possessing a depth that is difficult to replicate.
Matrix and Veining Patterns
Both stones can display a matrix (the host rock material), but their patterns differ. Howlite's veining is usually thin, erratic, and often appears as a fine, dark web against a lighter background. This veining is inherent to the stone's natural formation.
Turquoise matrix, often called the "spiderweb matrix" in high-grade pieces, can range from fine lines to thicker patches. The matrix material itself varies, including limonite (brown/black), sandstone (tan), or chert (gray). Unlike howlite, the matrix in turquoise is often integrated into the stone's color, sometimes creating pockets or streaks of contrasting material rather than just surface-level veining.
Luster and Surface Texture
Howlite typically has a matte, chalky, or sub-vitreous (glass-like) luster when polished. Its surface can feel slightly porous or waxy to the touch, especially in unpolished or lower-grade pieces. This porosity makes it an excellent candidate for dyeing.
Turquoise, when polished, exhibits a waxy to sub-vitreous luster, often described as having a smooth, slightly greasy feel. High-quality turquoise has a dense, non-porous surface, making it less absorbent than howlite. While it can also be porous, particularly lower-grade material, it generally has a finer texture than howlite.
Physical and Chemical Properties
Beyond visual cues, objective scientific properties offer definitive differentiation.
Hardness on the Mohs Scale
This is one of the most reliable indicators. Howlite is relatively soft, with a Mohs hardness of 3.5. This means it can be scratched by a steel knife or even a copper coin. Its softness makes it prone to scratching and abrasion over time.
Turquoise is significantly harder, rating between 5 and 6 on the Mohs scale. This places it in a similar range to materials like apatite or feldspar, making it more durable and resistant to everyday wear and tear compared to howlite. A genuine turquoise piece will not scratch easily with common household items.
Specific Gravity and Density
Specific gravity measures a stone's density relative to water. While not easily tested without specialized equipment, the difference exists:
- Howlite: Specific gravity ranges from 2.53 to 2.59. It feels relatively light for its size.
- Turquoise: Specific gravity ranges from 2.60 to 2.80. It generally feels denser and heavier than howlite of comparable size.
This subtle difference in density contributes to the overall "feel" of the stone, with genuine turquoise often feeling more substantial.
Porosity and Treatment Susceptibility
Howlite is naturally quite porous, which is why it readily accepts dyes. This porosity also means it can absorb oils, dirt, and other substances over time, potentially altering its appearance.
Natural turquoise varies in porosity. Higher-grade material is denser and less porous, while lower-grade turquoise can be quite porous. Due to its porosity, much of the turquoise on the market is "stabilized" with resins to enhance durability, color, and prevent absorption. This treatment is widely accepted but should be disclosed.
Pro Tip: To check for dyed howlite, gently rub an inconspicuous area with a cotton swab dipped in acetone (nail polish remover). If color transfers to the swab, it's likely dyed howlite or another treated material. This test should be performed with caution, as it can damage some finishes or treatments.
Commercial Context and Value
The distinction between howlite and turquoise carries significant commercial implications, primarily regarding value and ethical sourcing.
Cost and Availability
Howlite is an abundant mineral, making it inexpensive to mine and process. Its low cost, combined with its ability to be dyed, makes it a popular and affordable alternative to more precious stones. It is widely available in various forms, from beads to carvings.
Natural turquoise, particularly high-grade, un-stabilized material with desirable color and matrix, is considerably rarer and therefore much more expensive. Its value is influenced by factors such as origin (e.g., Persian, Sleeping Beauty), color saturation, and the quality of its matrix. Stabilized turquoise is more affordable than natural, untreated turquoise but still commands a higher price than howlite.
Imitation and Misrepresentation
The practice of dyeing howlite to imitate turquoise is widespread. This imitation allows jewelers and crafters to offer products with a turquoise-like appearance at a fraction of the cost. However, misrepresenting dyed howlite as natural turquoise is unethical and misleading. Understanding the differences empowers consumers to make informed purchasing decisions and ensures fair trade practices.
Making an Informed Choice
When evaluating items labeled as turquoise, consider the following:
- Price Point: If the price seems too good to be true for natural turquoise, it likely is.
- Color Uniformity: Unnaturally uniform or bright blue colors with perfectly consistent veining can be a red flag for dyed howlite.
- Scratch Test (Cautious): If you have a known piece of genuine turquoise or howlite, a gentle scratch test on an inconspicuous area can reveal differences in hardness, but this can damage the piece.
- Reputable Sellers: Purchase from vendors who are transparent about their materials and disclose any treatments or enhancements.
Ultimately, appreciating both howlite and turquoise for their individual qualities is key. Howlite offers an attractive, affordable option, especially when dyed, while genuine turquoise provides a unique, valuable gemstone with a rich history.
Frequently Asked Questions
Is howlite a natural stone? Yes, howlite is a naturally occurring mineral composed of calcium borosilicate hydroxide. It is found in evaporite deposits and is typically white with gray or black veining.
How can I tell if my turquoise is real or fake? Real turquoise is harder (Mohs 5-6), denser, and its color often has a natural depth. Fake turquoise, often dyed howlite, is softer (Mohs 3.5), lighter, and may show signs of dye near scratches or imperfections. A gentle acetone test can reveal surface dyes.
Does howlite change color over time? Natural howlite's white color is stable. However, dyed howlite may fade or change color over time, especially with exposure to sunlight, chemicals, or repeated handling, as the dye can degrade or wear off.
Can turquoise be dyed? While less common than dyeing howlite, some lower-grade, highly porous turquoise can be dyed to enhance its color. However, stabilization with resin is a more prevalent and accepted treatment for natural turquoise to improve its durability and appearance.
