Guatemala has been the focus of significant media attention since the recent announcement of a “jade lode as big as Rhode Island” (see W. J. Broad, “Found in the Guatemalan wilds…,” New York Times, May 22, 2002, pp. A1, A10). This discovery is particularly significant because one of the new areas contains several large boulders of jadeite with narrow bands of bluish green and greenish blue that are jewelry quality. Local jade hunters discovered the boulders in the mid-1990s, in rugged terrain about 40 km west of Chiquimula. The significance of the discovery was recognized more recently, following the exposure of new jadeite outcrops and alluvial boulders by torrential rains that accompanied Hurricane Mitch in October 1998.

These contributors have been involved in field exploration for Guatemalan jadeite with Ventana Mining Co. since January 2001. The discovery area reported by the New York Times lies in the Motagua river valley about 80 km northeast of Guatemala City. All of the jade deposits known in Guatemala are found within or near the Motagua fault zone (MFZ), an east-west–trending boundary between the North American and Caribbean tectonic plates; this area is active today as a zone of left-lateral faults. Along and adjacent to this zone, numerous sheared serpentinite bodies are present in an area 10–40 km wide and 100 km long. Jadeite occurs within the serpentinites as veins, lenses, and pods a few meters wide and up to tens, or even hundreds, of meters long. These primary jadeite bodies are the sources of the alluvial boulders found throughout the region. The jadeite is thought to have crystallized directly from a hydrous fluid at pressures of 5–12 kbar and temperatures of 200°–450°C (V. B. Sisson et al., “Jadeitite and eclogite occurrences along the Motagua Suture Zone, Guatemala,” Programme with Abstracts, 18th General Meeting of the International Mineralogical Association, Edinburgh, Scotland, September 1–6, 2002, pp. 221–222).

The recent finds of bluish green jadeite are similar to the type associated with royalty in the Olmec culture. As such, these contributors describe this new material as “Olmec Imperial” jadeite (right). It has also been called the local term in Spanish for “green vein” in the field. From an examination of 12 polished samples, we noted that this material shows a significantly darker tone in reflected light compared to its appearance in transmitted light, and was translucent up to a thickness of 5 mm. Spot R.I. values were 1.65 to 1.68 and the S.G. (determined hydrostatically) ranged from 3.27 to 3.34.

A different material (right), termed “New Blue” jadeite by these contributors has been found for the first time in the field. This bluish green to greenish blue jadeite is called various names by local prospectors, including the terms in Spanish for “celestial blue” and “window blue.” This material is entirely different from the “Olmec Blue” jade (a green jadeite, typically of low saturation) previously described in the gemological and archaeological literature (see, e.g., R. Seitz et al., “‘Olmec Blue’ and formative jade sources: New discoveries in Guatemala,” Antiquity, Vol. 75, 2001, pp. 687–688).

Dr. Robert Coleman of Stanford University has confirmed from petrographic and geochemical analysis that the New Blue material is 95% jadeite with small amounts of phengite mica, sphene, albite, and zircon (pers. comm., 2002). This is consistent with our examination of five polished samples, which yielded S.G. values from 3.32 to 3.34 and R.I.’s of 1.66 to 1.68. The material was translucent up to a thickness of 12 mm. The samples were dark bluish green in reflected light, and medium-light bluish green to greenish blue in transmitted light. The blue color component is due to Fe²⁺–Ti⁴⁺ intervalence charge transfer, whereas the green is produced through Fe²⁺ and Fe³⁺ absorptions (G. Harlow, pers. comm., 2002).

Recovery of both the Olmec Imperial and the New Blue jadeite by local jade hunters has historically been only from creek beds and alluvial terrace deposits downstream of the giant boulders. The local jade hunters sell most of their rough to the several jewelry manufacturers in Antigua, Guatemala. These manufacturers sell almost all of their jewelry to the local tourist trade.

John G. Cleary and
William R. Rohtert (william.rohtert@ventanamining.com)
Ventana Mining Company, Reno, Nevada