Howlite is a borate mineral (calcium borosilicate hydroxide) discovered in 1868. It forms within evaporite deposits, often found alongside gypsum. Identifying this stone requires examining its visual features and physical properties, which is important because it is frequently used in the jewelry market in both its natural and altered states.
The Natural Appearance of Howlite
Howlite typically forms in irregular masses or nodules, which often possess a rough, uneven texture that has been compared to the look of cauliflower. The primary color of the mineral itself is opaque white, off-white, or a light grayish-white. This coloration is generally uniform. The natural mineral is opaque, meaning light does not pass through it, and it rarely forms in distinct, visible crystals.
The Defining Matrix Pattern
The most recognizable feature of Howlite is the characteristic veining, or matrix, that runs through the white base material. These veins appear as thin, erratic lines, often creating a web-like or spiderweb pattern across the stone’s surface. The matrix color is typically dark grey, black, or occasionally brown, providing a strong contrast to the pale background. The density and thickness of this dark veining can vary significantly, ranging from faint streaks to a pronounced, marbled appearance.
Physical Characteristics
Howlite is characterized by its relatively low hardness, scoring approximately 3.5 on the Mohs scale of mineral hardness. This softness means the stone is susceptible to scratches and abrasion, which affects its use and durability in jewelry. The mineral’s texture is often described as porous or chalky, which contributes to its ability to absorb substances. When polished, Howlite displays a luster that ranges from sub-vitreous (slightly glassy) to dull or earthy.
How Howlite is Commonly Used and Altered
The porous nature and pale color of Howlite make it an ideal material for commercial alteration, especially through dyeing. It is frequently dyed vibrant shades of blue or green to imitate more expensive stones, most notably Turquoise. When dyed blue, it is sometimes sold under trade names such as “blue howlite” or “turquenite.” To distinguish a dyed specimen, observe the color for unnaturally uniform saturation. The dye may also be concentrated in the dark veins, making them appear overly intense. In some cases, the dye only penetrates the surface, and a simple scratch or rub may reveal the white interior or cause the color to bleed.