Brendan M. Laurs

PEZZOTTAITE FROM AMBATOVITA, MADAGASCAR: A NEW GEM MINERAL

Pezzottaite, ideally Cs(Be_2Li)Al_2Si_6O_(18), is a new gem mineral that is the Cs,Li–rich member of the beryl group. It was discovered in November 2002 in a granitic pegmatite near Ambatovita in central Madagascar. Only a few dozen kilograms of gem rough were mined, and the deposit appears nearly exhausted. The limited number of transparent faceted stones and cat’s-eye cabochons that have been cut usually show a deep purplish pink color. Pezzottaite is distinguished from beryl by its higher refractive indices (typically n_o=1.615–1.619 and n_e=1.607–1.610) and specific gravity values (typically 3.09–3.11). In addition, the new mineral’s infrared and Raman spectra, as well as its X-ray diffraction pattern, are distinctive, while the visible spectrum recorded with the spectrophotometer is similar to that of morganite. The color is probably caused by radiation-induced color centers involving Mn^(3+).

Liddicoatite Tourmaline From Anjanabonoina, Madagascar

28 LIDDICOATITE FROM MADAGASCAR GEMS & GEMOLOGY SPRING 2002 three lithium tourmalines with the general formula (Ca,Na,K, )(Li,Al)3Al6Si6O18(BO3)3(OH)3(OH,F), which are defined on the basis of their X-site occupancy: Ca = liddicoatite, Na = elbaite, and a vacant ( ) X site = rossmanite. Elbaite is the most abundant gem tourmaline, whereas rossmanite has so far been identified from few localities (Johnson and Koivula, 1998b; Selway et al., 1998), and typically is not of gem quality. However, neither can be separated from liddicoatite without quantitative chemical analysis. Therefore, in this article we use the group name tourmaline to refer to material that has not been chemically analyzed. Although liddicoatite is well characterized mineralogically, little has been published about the history, sources, and gemology of this tourmaline species in particular. This article focuses on liddicoatite from Madagascar—which is the principal historic source— and in particular on the Anjanabonoina pegmatite, By Dona M. Dirlam, Brendan M. Laurs, Federico Pezzotta, and William B. (Skip) Simmons

Copper-bearing (Paraíba-type) tourmaline from Mozambique

Copper-bearing tourmaline from Mozambique was first recovered in 2001, but its Cu content was not recognized until 2003, and it was not widely sold with its Mozambique origin disclosed until 2005. It has been mined from alluvial deposits in an approximately 3 km2 area near Mavuco in the eastern portion of the Alto Ligonha pegmatite district. Most of the production has come from artisanal mining, with hand tools used to remove up to 5 m of overburden to reach the tourmaline-bearing layer. The stones exhibit a wide range of colors, typically pink to purple, violet to blue, and blue to green or yellowish green. Heat treatment of all but the green to yellowish green stones typically produces Paraiba-like blue-to-green hues by reducing absorption at ∼520 nm caused by the presence of Mn3+. The gemological properties are typical for Cu-bearing tourmaline (including material from Brazil and Nigeria); the most common inclusions consist of partially healed fractures and elongate hollow tubes. With the exception of some green to yellow-green stones, the tourmalines examined have relatively low Cu contents and very low amounts of Fe and Ti. Mechanized mining is expected to increase production from this region in the near future.

An Update on "Paraíba" Tourmaline from Brazil

260 “PARAÍBA” TOURMALINE GEMS & GEMOLOGY WINTER 2001 Milisenda 2001; Smith et al., 2001; Zang et al., 2001). The colors of some cuprian elbaites can be changed by heat treatment, and some are fracturefilled to improve their apparent clarity. During the 1990 Tucson gem show, prices for this material skyrocketed from a few hundred dollars to over

Ruby and sapphire from Jegdalek, Afghanistan

2,000 per carat in just four days (Federman, 1990; Reilly, 1990). Restricted availability due to limited production over much of the past decade has only added to the value and mystique of these cuprian elbaites. In recent years, 3+ ct finequality blue to green-blue faceted tourmalines from the São José da Batalha area have sold for

Chrysoprase and Prase Opal from Haneti, Central Tanzania

20,000 per carat in Japan (R. Van Wagoner, pers. comm., 2001). Until recently, difficulties involving legal ownership caused restricted access to the Mina da Batalha. In August 2000, however, the authors were able to visit the locality and gather first-hand information on the geology, current mining activities, and tourmaline production. During this same trip, we also By James E. Shigley, Brian C. Cook, Brendan M. Laurs, and Marcelo de Oliveira Bernardes

YELLOWISH GREEN DIOPSIDE AND TREMOLITE FROM MERELANI, TANZANIA

GEMS & GEMOLOGY Summer 2000 he gem mines of Afghanistan are some of the oldest in the world. The lapis lazuli mines at Sar-eSang, in the Badakhshan region, have been worked for at least 6,500 years (see, e.g., Wyart et al., 1981). Today, Afghanistan continues to be an important source of various gem minerals—including emerald, ruby, sapphire, aquamarine, tourmaline, and spodumene (see, e.g., Bowersox and Chamberlin, 1995). Yet relatively little is known about many of the gem localities. This article reports on the only known source of ruby in Afghanistan: the Jegdalek region. A historical review, the geology, mining methods, and current production of gem corundum (figure 1) from Jegdalek are given below, together with the results of our research on the gemological properties of this material.

Geological setting and petrogenesis of symmetrically zoned, miarolitic granitic pegmatites at Stak Nala, Nanga Parbat-Haramosh Massif, northern Pakistan

GEMS & GEMOLOGY WINTER 2009 271 hrysoprase and prase opal are nickel-containing green varieties of chalcedony and nonplay-of-color (common) opal, respectively. Both have been used as gem materials for thousands of years. Chrysoprase was described as being the “most prized” type of chalcedony by Webster (1994, p. 233). Central Tanzania is an important contemporary source of both these gems. The Tanzanian materials were first briefly described by Gubelin (1975, pp. 76–78) and Schmetzer et al. (1976). These reports were followed by a characterization of the green prase opal by Koivula and Fryer (1984), and a more detailed study of the chrysoprase by Kinnunen and Malisa (1990). This article briefly describes the geology, mining, and gemological characteristics of high-quality Tanzanian chrysoprase and prase opal from the Iyobo Mountain mine near Haneti (figure 1). This mine is operated by Dimitri Mantheakis, who hosted two of the authors (JES and BML) there in May 2008. Although both materials have also been found in several other parts of the world (table 1), Tanzania is probably the most important source of chrysoprase after Australia.

Tourmaline: The Kaleidoscopic Gemstone

GEMS & GEMOLOGY SUMMER 2007 t the 2006 Tucson gem shows, Steve Ulatowski showed one of the authors (BML) some yellowish green crystals that he purchased as diopside while on buying trips to Tanzania in August and November 2005. The material was reportedly produced during this time period from Block D at Merelani, in the same area that yielded some large tsavorite gem rough (see Laurs, 2006). Mr. Ulatowski obtained 1,200 grams of the green crystals, mostly as broken pieces ranging from 0.1 to 50 g (typically 1–5 g). More recently, in May 2007, he obtained some additional pieces of gem-quality material weighing 0.1–2 g. The “mint” green color is quite attractive, but most of the rough is not cuttable due to the presence of cleavage planes and, in some cases, the flat morphology of the crystal fragments. In 2006, Mr. Ulatowski was informed by a few of his customers that the flatter crystals might be tremolite, rather than diopside. This was consistent with the diamond-shaped cross-section of these crystals (typical of an amphibole), which was distinct from the blocky cross-section (typical of diopside, which is a pyroxene) shown by other crystals in the parcels. Mr. Ulatowski loaned one example of both types of crystals to GIA for examination (figure 1), and we also