gems, garnet, pyrope-almandine, rhodolite, star garnet, star rhodolite, Tanzania

This article describes the first reported occurrence of asteriated rhodolite garnet from Tanzania and details the specimen’s gemmological properties. Acicular rutile crystals are well-known inclusions in almandine garnets (Webster, 1983; Gübelin and Koivula, 1986; Liddicoat, 1987), and when fashioned en cabochon, stones with a relatively dense and even distribution of these needle-like inclusions may exhibit asterism, typically as a four- or six-rayed star. Sources of star almandine garnet include India (Webster, 1983; Rohrbach, 1986) and the Emerald Creek area of Idaho, USA (Zeitner, 1986; Rohrbach, 1986). Rhodolite, a reddish-purple to purple garnet composed of a mixture of almandine and pyrope, was first described from North Carolina, USA (Hidden and Pratt, 1898), and is also found in Sri Lanka (Webster, 1983), a major commercial source (Federman, 1984). In recent decades, African localities such as Zimbabwe (Campbell, 1972), Madagascar (Campbell, 1973), and Tanzania (Phillips, 1962; Sinkankas, 1968; Sarofim, 1970; Pough, 1973) have also produced rhodolite, with Tanzania now serving as an important commercial source (Federman, 1984). Like almandine, rhodolite from several sources may contain acicular rutile inclusions (Campbell, 1972; Webster, 1983), though few references have noted these inclusions producing asterism in rhodolite (Rohrbach, 1986). The authors recently examined a rhodolite garnet cabochon that displayed a four- or six-rayed star, depending on the viewing angle. The stone was cut from rough purchased and fashioned by Mr. Barton Curren of Glyptic Illusions, Topanga, California, USA, from a Tanzanian parcel reportedly originating from the Kangala mine. According to Curren, the rough was relatively inexpensive due to its higher inclusion content compared to other Tanzanian rhodolite he had previously acquired.