San Carlos peridot is the gem-quality forsterite-rich olivine extracted from upper-mantle xenoliths in the basalt flow at Peridot Mesa, on the San Carlos Apache Reservation in southeastern Arizona. It is the principal source of peridot sold in the United States market and one of the more significant working peridot deposits worldwide. The stones are reliably untreated, available in consistent commercial volumes, and offered at moderate price points that have made them the default for peridot in American jewellery for the past three decades. The variety is best understood as a commercial workhorse rather than as a rarity: well-cut stones of medium-toned yellowish-green to olive-green colour are routinely available in sizes from one to ten carats, with larger stones present but increasingly scarce.

Origin and material

The peridot at San Carlos derives from olivine xenoliths — fragments of the upper mantle of approximately fifty to one hundred kilometres depth — that were entrained in basaltic magma during the eruption of Peridot Mesa approximately one to two million years ago. The xenoliths are predominantly dunite (nearly pure olivine) with subordinate clinopyroxene, and the gem-quality olivine within them is forsterite-rich, with magnesium considerably exceeding iron in the olivine solid solution. The mineral chemistry produces the characteristic colour: yellowish-green through grass-green to olive-green, with the most desirable stones showing a clean medium-toned green free of excessive yellow or brown undertones.

The stones

San Carlos peridot is typically eye-clean to lightly included, with the characteristic disc-shaped 'lily-pad' inclusions that form around small crystal inclusions within the olivine and are diagnostic of natural peridot under magnification. Other inclusions include small chromite crystals and occasional negative crystals. Cut stones range from melee sizes through to ten carats commonly, with stones over fifteen carats produced in smaller numbers and stones over twenty-five carats rare. The strong birefringence (about 0.036) produces a visible doubling of back facets through the table, which is a diagnostic identification feature and which the cutter must accommodate by orienting the rough so that the doubling is minimised when viewed face-up.

Heat treatment is not used. The colour is the natural product of the mineral chemistry and requires no enhancement, which gives San Carlos peridot a clean disclosure profile relative to many other coloured stones in the same price tier.

Comparative quality

Within the global peridot market, San Carlos sits in the middle commercial tier. The finest Pakistani Kohistan peridot, with its more saturated and slightly bluer-green colour, commands higher prices for matched fine stones; the historic Egyptian Zabargad material, although now of largely historical importance, remains the iconic origin reference. Burmese peridot from Mogok produces some very fine stones in larger sizes. San Carlos material does not generally match the finest Kohistan or Burmese stones in colour saturation, but it offers consistency, supply, and price advantages that make it the preferred choice for commercial bridal and decorative jewellery in the American market.

Pricing and trade

Pricing for San Carlos peridot at the commercial level ranges from low double-digit dollars per carat for smaller, average-quality stones up to several hundred dollars per carat for fine large stones. The pricing tier is moderate enough to support widespread use in mid-priced commercial jewellery without requiring the close margin management that more expensive coloured stones demand. The supply is sufficiently consistent that working jewellers can plan production around availability rather than treating it as an opportunistic stock.

San Carlos origin is occasionally noted on independent laboratory reports based on the inclusion characteristics typical of the deposit, though origin is rarely a determining factor in pricing at the commercial level. For high-end peridot work, where buyers may pay a premium for documented origin, Pakistani or Burmese provenance is more often the marketed point.

Setting and care

Peridot's hardness of 6.5 to 7 makes it acceptable for ring use but not the most durable choice. Bezel and protected settings are preferable to open prongs for daily-wear rings. Cleaning should be by mild soap and warm water; ultrasonic and steam cleaning are not recommended because of peridot's sensitivity to thermal shock and to potential damage from any surface-reaching feathers.

In the trade

For independent jewellers, San Carlos peridot represents the most reliable sourcing for moderate-priced peridot jewellery in North America. The stones are typically purchased through wholesale lapidary houses or directly through tribal-managed lapidary operations, with sufficient documentation of origin where buyers want to specify San Carlos provenance. The material's consistency makes it suitable for jewellery production at scale, and its untreated status simplifies disclosure relative to many other coloured stones at the same price point.

Further reading

• GIA — Peridot reference
• GIA Gems & Gemology — peridot origin and inclusion studies
• International Gem Society — peridot reference