The Foutz process is a proprietary stabilisation treatment applied to turquoise, in which a clear polymer resin is introduced under pressure into the stone's natural pore structure to consolidate friable material, improve surface hardness, deepen colour saturation, and produce a more receptive polish. Developed in the United States — associated with the Foutz family, long-established traders in Native American and Southwestern jewellery — the process belongs to the broader category of polymer impregnation treatments that have become standard practice in the commercial turquoise trade. It is analogous in intent and general methodology to the better-known Zachery process, though the specific chemistry and procedural parameters of each remain proprietary. Reputable dealers and gemmological laboratories disclose the Foutz treatment, and its presence can be confirmed through infrared spectroscopy and careful magnification.

Why Turquoise Requires Stabilisation

Turquoise — a hydrated copper aluminium phosphate, chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O — is inherently porous and ranges widely in hardness, from approximately 5 to 6 on the Mohs scale. The finest gem-quality material, such as that historically recovered from the Nishapur district of Iran or from the Sleeping Beauty mine in Arizona, is sufficiently dense and hard to be cut and polished without intervention. The great majority of commercially mined turquoise, however, is too soft, too porous, or too structurally fragile in its natural state to withstand lapidary work or sustained wear. Such material is described in the trade as chalk turquoise or simply as low-grade rough.

Untreated porous turquoise is susceptible to several forms of deterioration: absorption of skin oils, cosmetics, and perspiration can cause irreversible colour shifts toward green or brown; mechanical stress during cutting or setting can produce fractures along natural voids; and the surface may resist a stable polish, appearing dull or uneven. Stabilisation addresses all three vulnerabilities by filling the pore network with a consolidating medium.

The Stabilisation Procedure

In polymer stabilisation generally — and the Foutz process follows this broad framework — rough or pre-shaped turquoise is first cleaned and dried to remove moisture and surface contaminants from the pore channels. The material is then placed in a pressure vessel, where a vacuum is drawn to evacuate air from the pores. A liquid resin, typically a clear epoxy or acrylic polymer, is introduced and the pressure is raised to drive the resin throughout the stone's internal network. The impregnated material is subsequently cured, either thermally or by ultraviolet exposure depending on the resin system, causing the polymer to harden in place.

The result is a composite material: the turquoise mineral matrix is physically unchanged, but its voids are now occupied by a stable, inert polymer. Hardness increases modestly — treated stones typically approach the upper end of the natural turquoise hardness range — and the surface accepts a brighter, more consistent polish. Colour may appear marginally more saturated because the resin's refractive index is closer to that of the turquoise mineral than air, reducing light scattering from internal voids.

The Foutz process is distinguished from simple waxing or oiling — older and less durable surface treatments — by the depth and permanence of penetration. Wax and oil treatments can be reversed by gentle heat; polymer stabilisation of the Foutz type is effectively permanent under normal wearing conditions.

Detection and Laboratory Identification

Gemmological identification of polymer stabilisation in turquoise relies principally on two techniques. Infrared spectroscopy (FTIR) is the most definitive: the polymer introduces characteristic absorption bands not present in untreated turquoise, and modern FTIR instruments can detect even small quantities of resin within the stone's matrix. The GIA Gem Laboratory and other major laboratories routinely employ FTIR for this purpose.

Under magnification, stabilised turquoise may show a slightly plastic or resinous lustre in surface pits or along matrix boundaries, and the polish may appear unusually uniform for material that would otherwise be expected to show porosity-related surface irregularities. Long-wave ultraviolet fluorescence can also be informative: many resins fluoresce in a manner inconsistent with natural turquoise, though this test alone is not conclusive.

It is worth noting that the Foutz process, like the Zachery process, does not alter the chemical composition of the turquoise mineral itself, which complicates detection by methods that rely solely on elemental analysis. FTIR remains the standard.

Trade Disclosure and Market Standing

Within the Southwestern American jewellery trade — where turquoise has profound cultural significance for Navajo, Zuni, Pueblo, and other Indigenous artisans and communities — disclosure of treatment status is both an ethical obligation and, in many contexts, a legal one. The Federal Trade Commission's guidelines on jewellery marketing require that material enhancements affecting value be disclosed to buyers. Reputable dealers handling Foutz-treated turquoise are expected to identify it as stabilised on invoices and labels.

The hierarchy of value in the turquoise market is well established. Natural, untreated turquoise of fine colour and sufficient hardness commands the highest prices, with premium material from historic Persian sources, Lander Blue (Nevada), or Bisbee (Arizona) reaching significant sums per carat. Stabilised turquoise — including Foutz-treated material — occupies a middle tier: it is genuine turquoise, not a simulant or synthetic, and it is widely accepted in commercial jewellery. Its value is, however, substantially lower than comparable untreated stones, reflecting both the treatment itself and the fact that stabilisation is most commonly applied to material that would not be commercially viable in its natural state.

Foutz-treated turquoise should be clearly distinguished from two lower categories: reconstituted turquoise, in which turquoise powder and fragments are bound together with resin to form a composite block (not genuine turquoise in the gemmological sense), and simulants such as dyed howlite or magnesite, which contain no turquoise mineral at all.

Care Considerations

Polymer-stabilised turquoise is more robust in everyday wear than untreated material, but it is not impervious to damage. Prolonged exposure to strong solvents — acetone, paint thinner, and similar chemicals — can degrade or discolour the resin matrix. Ultrasonic and steam cleaning are contraindicated, as vibration and heat may compromise the polymer. Gentle cleaning with a soft, damp cloth remains the recommended approach. The stone should be protected from sharp impacts, as the underlying turquoise mineral, despite stabilisation, retains its natural brittleness.

Further Reading

• Fritsch et al., "The Zachery Treatment of Turquoise," Gems & Gemology, Spring 1997 — GIA
• GIA Gem Encyclopedia: Turquoise
• AGTA: Turquoise — Consumer Information