Carico Lake Turquoise

Nevada's celebrated lime-green turquoise, prized for its zinc-rich chemistry and spiderweb matrix

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Carico Lake turquoise is a distinctive variety of natural turquoise mined from the Carico Lake deposit in Lander County, Nevada, distinguished above all by its vivid lime-green to blue-green colour. Unlike the sky-blue stones most commonly associated with turquoise, Carico Lake material owes its unusual hue to an elevated zinc content within the copper phosphate mineral structure — a geochemical circumstance that places it among the most recognisable and collectible turquoise varieties produced anywhere in North America. High-quality specimens, particularly those displaying a fine spiderweb matrix of dark brown limonite against a bright green ground, command significant premiums in the collector and lapidary markets.

Mineralogy and Colour Chemistry

Turquoise is a hydrated copper aluminium phosphate, with the idealised formula CuAl₆(PO₄)₄(OH)₈·4H₂O. In most deposits, copper is the dominant chromophore, producing the characteristic blue tones. At Carico Lake, however, zinc substitutes for a portion of the copper in the crystal lattice, shifting the absorption characteristics and yielding colours that range from a pale, almost chartreuse green through bright lime-green to a saturated blue-green. When zinc substitution is near-complete, the resulting mineral approaches the zinc-dominant end-member faustite, though most Carico Lake material is properly described as zinc-rich turquoise rather than true faustite. The degree of zinc substitution varies nodule by nodule within the deposit, which accounts for the colour range seen across different pieces from the same mine.

The hardness of Carico Lake turquoise typically falls in the range of 5 to 6 on the Mohs scale, consistent with turquoise generally, though the porosity of individual pieces varies considerably. More porous material is susceptible to colour change from skin oils and perspiration — a consideration relevant to both the jeweller and the end wearer.

The Deposit and Its History

The Carico Lake mine sits within the turquoise-bearing volcanic terrain of Lander County, a region of central Nevada that has historically been one of the most productive turquoise-producing areas in the United States. Nevada as a whole accounts for the majority of American turquoise production, with notable deposits also found at Royston, Lone Mountain, and the Godber-Burnham mine, among others.

Commercial working of the Carico Lake deposit began intermittently in the 1970s. The mine has changed hands over the decades and is today privately held, with production remaining limited and irregular. This restricted supply is a significant factor in the material's market value: unlike some Nevada deposits that were heavily worked through the mid-twentieth century, Carico Lake has never been subjected to large-scale industrial extraction, and the volume of high-grade material reaching the market at any given time is modest. Miners have worked the deposit using small-scale open-cut and shallow underground methods typical of turquoise operations throughout the American Southwest.

Matrix and Appearance

One of the most visually compelling features of Carico Lake turquoise is its matrix — the host rock or secondary minerals that remain intergrown with the turquoise nodules after cutting. At Carico Lake, the matrix most commonly takes the form of dark brown to black limonite veining that spreads across the stone in fine, branching networks. When this veining is particularly intricate and evenly distributed, the pattern is described in the trade as spiderweb matrix, a term applied across several Nevada localities but especially associated with Carico Lake material.

Collector preference for matrix versus clean material varies. Some buyers prize a fine spiderweb pattern as evidence of natural origin and as an aesthetic feature in its own right; others prefer stones with minimal or no matrix, in which the lime-green colour can be appreciated without interruption. Completely matrix-free Carico Lake turquoise of strong colour is relatively scarce and commands the highest prices. Stones with a balanced, symmetrical spiderweb pattern over a vivid green ground are also highly regarded.

The colour of Carico Lake turquoise is its most immediately recognisable attribute. The lime-green hue is sufficiently distinctive that experienced dealers and collectors can often identify the origin of a stone at sight, though definitive provenance attribution requires gemological testing and, ideally, knowledge of the material's chain of custody. Colour alone is not a reliable proof of origin, since other zinc-rich turquoise deposits — including some in Mexico and China — can produce superficially similar greens.

Treatment and Stability

As with turquoise from virtually all localities, Carico Lake material is subject to a range of treatments intended to improve apparent colour, lustre, or durability. The most common treatment applied to porous turquoise is stabilisation, in which a colourless resin or polymer is impregnated under vacuum into the stone's pore structure. Stabilised material is more resistant to colour change and easier to polish to a high lustre, but it is considered less valuable than untreated natural turquoise of equivalent colour and quality.

A further treatment, sometimes called colour enhancement or dyeing, involves the introduction of colourants alongside or instead of a neutral resin. Dyed turquoise is considered a separate commercial category from both natural and stabilised material and must be disclosed. In the context of Carico Lake turquoise specifically, the distinctive lime-green colour has made it a target for imitation: dyed howlite, dyed magnesite, and dyed lower-grade turquoise from other localities have all been offered in the market under the Carico Lake name. Buyers seeking confirmed natural, untreated Carico Lake turquoise are advised to obtain material with documented provenance or to request testing by a recognised gemological laboratory.

Gemological identification of treatment status in turquoise typically involves infrared spectroscopy (FTIR), which can detect the presence of polymer resins, and long-wave ultraviolet fluorescence observation, which may reveal dye concentrations in surface fractures. The Gemological Institute of America and other major laboratories offer turquoise identification and treatment-disclosure reports.

In the Trade

Carico Lake turquoise occupies a well-defined niche in the American turquoise market. It is particularly sought after by collectors of natural, high-grade American turquoise, by Native American silversmiths working in traditional and contemporary jewellery forms, and by lapidaries who appreciate the challenge and reward of cutting a material with such a distinctive colour profile. The lime-green tone pairs effectively with both oxidised sterling silver — the dominant metal in Southwestern jewellery traditions — and with yellow gold, where the colour contrast is especially striking.

Pricing for Carico Lake turquoise reflects both quality and treatment status. Natural, untreated material of strong lime-green colour with a fine spiderweb matrix or clean face can reach prices comparable to high-grade Sleeping Beauty or Lander Blue turquoise — among the most valued American varieties. Stabilised Carico Lake material is more widely available and more moderately priced, though still commands a premium over generic stabilised turquoise by virtue of its colour. Cabochons cut from top-grade natural Carico Lake rough have been documented at wholesale prices well above those of most other Nevada localities, reflecting both the material's scarcity and its aesthetic reputation.

The mine's limited and irregular production means that the supply of new rough entering the market is unpredictable. Much of the Carico Lake turquoise currently available in the trade derives from existing stocks of rough or finished stones rather than from active mining. This situation is common across many of the historic American turquoise deposits, where the combination of exhausted or marginal ore bodies, high operating costs, and complex land-tenure arrangements has curtailed production significantly since the mid-twentieth century.