lipo in Yunnan, China; Panjshir, Afghanistan; and Gandao, Pakistan. In this article, we refer to "vanadian emeralds" as those that contain more vanadium than chromium, even when the vanadium content is somewhat low. The mechanisms of beryl coloration by Cr and V are very similar (Burns, 1993;Schwarz and Schmetzer, 2002); in 1988, after many years of controversy, vanadium joined chromium as an accepted coloring agent for emerald (CIBJO, 1988). HISTORICAL BACKGROUNDThe Byrud emerald deposit was probably discovered in the 1860s. During these early years, emerald specimens were obtained by several European natural history museums, including Stockholm in
Heulandite-Ba, ideally (Ba,Ca,Sr,K,Na) 5 Al 9 Si 27 O 72 •22H 2 O, is a new zeolite species in the heulandite series, occurring as an accessory mineral in hydrothermal veins of the Kongsberg silver deposit type at the Northern Ravnås prospect, southern Vinoren, 14 km NNW of Kongsberg town, Kongsberg ore district, Flesberg community, Buskerud county, Norway. The mineral has also been found at the Bratteskjerpet mine, Saggrenda near Kongsberg, and in hydrothermal veins in quartzite at Sjoa in Sel community, Oppland county. Heulandite-Ba occurs as well developed, thick tabular, trapezoidal crystals up to 4 mm across, showing the forms {100}, {010}, {001}, 111} and {201}. The mineral is colourless to white, rarely very pale yellowish white or pale beige, with a white streak; transparent to translucent, with a vitreous lustre, pearly on {010}. The mineral has a perfect {010} cleavage; subconchoidal to uneven fracture. It is non-fluorescent in long-or shortwave ultraviolet light. The Mohs' hardness is 3½; D meas = 2.35(1) and D calc = 2.350 g/cm 3. Heulandite-Ba is biaxial positive with n [ = 1.5056(5), n q = 1.5064(5) and n * = 1.5150(5); 2 = 0.0094, n (mean) = 1.5090. 2V * (calc) = 34.1°, 2V * (meas) = 38(1)°; distinct dispersion, r > v; [ , c varying from ≅ 39°to ≅ 51°in obtuse angle q , * = b. An average of 14 electron microprobe analyses on heulandite-Ba from the Northern Ravnås prospect, Kongsberg, gave SiO 2 54.26, Al 2 O 3 15.27, MgO <0.1, CaO 2.65, SrO 1.03, BaO 12.76, Na 2 O 0.34, K 2 O 0.58, H 2 O 13.1 (from TGA), total 99.99, corresponding to (Ba 2.49 Ca 1.41 Sr 0.30 K 0.37 Na 0.33) 7 4.90 Al 8.96 Si 27.00 O 72.00 •21.75H 2 O on the basis of 72 framework oxygen atoms. Chemical zoning is frequent, with transitions to heulandite-Ca and heulandite-Sr. Heulandite-Ba is monoclinic, C2/m, with a = 17.738(3), b = 17.856(2), c = 7.419(1) Å, q = 116.55(2)°, V = 2102.0(7) Å 3 , Z = 1. The strongest five X-ray diffraction lines of the powder pattern [d in Å(I)(hkl)] are: 2.973(100)(151), 3.978(97)(131), 7.941(66)(200), 4.650(66)(-131), 2.807(65)(-621). The crystal structure refinements (R = 3.5 %) of heulandite-Ba were done in space groups C2/m, Cm, C2, and C1, but refinements in space groups with lower symmetry than C2/m did not improve the structural model.
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