Three samples of dalmatian stone, including a rough sample, bracelet, and pendant from an unknown locality, were purchased during the International Exhibition and Trade Fair of Minerals, Fossils, and Jewellery at the Krakow University of Economics in Poland. To accomplish this we applied microscopic observations in transmitted light, scanning electron microscopy, Raman microspectroscopy, and chemical analysis. The aim of this work is to determine the detailed mineralogical composition of dalmatian stone, classify it properly, and discuss potential locations of the rock’s outcrops proposed by distributors of the material. Moreover, the source of this gemstone has not yet been specified (Dietrich, 2009). On the other hand, Campos-Venuti (2012) considered it a variety of devitrified rhyolite and classified it as “rhyolitic jasper.” In contrast, some informational websites on various gemstones (e.g., indicate that the black spots in dalmatian stone are composed of tourmaline-group minerals. Based only on microscopic observations, Bruder (2006) recognized dalmatian stone as an aplite, consisting predominantly of quartz, feldspars (albite and microcline), and Fe-riebeckite. Published information on dalmatian stone and its mineralogical composition is quite meager. The surface of the rock is sometimes covered by red to brown iron oxide/hydroxide minerals. The diameter of these black spots usually does not exceed 4 mm. The rock mass strongly contrasts with the black to greenish spherical assemblages of minerals that are responsible for the unique dalmatian pattern. Dalmatian stone consists of a white to grayish rock mass devoid of larger phenocrysts, with small crystals of quartz visible to the unaided eye. “Dalmatian jasper,” also known as “dalmatian stone,” is a misnomer if we consider the gemological definition of jasper or even other spotted stones mentioned in the literature (some of which were presented in the previous paragraph). In some cases, more detailed mineralogical and petrological studies are necessary to determine the particular type of material. Except for silica, most also contain some admixtures such as iron oxides/hydroxides, feldspars, and epidotes (Żaba, 2010). In general, all jasper types have specific physical, chemical, and aesthetic properties that make them a valuable material for jewelry. Examples include, respectively, radiolarites such as mookaite jasper (Campos-Venuti, 2012), quartzites such as Sioux Falls jasper (Dietrich, 2009), and rhyolites such as orbicular jasper and picture jasper (Żaba, 2010 Polk, 2012). Hence, the jasper group is characterized by sedimentary, metamorphic, or igneous rocks. Götze (2010) defined it as a mixture of microcrystalline silica with iron oxide and illite, while Kievlenko (1980) classified it as a metamorphic or metasomatic material. Manutchehr-Danai (2010) considered jasper a dense, translucent to opaque impure variety of chalcedony or chert. In addition, the nomenclature and classification of jaspers are not well coordinated in gemology and petrology (Kostov, 2010). Unfortunately, the term “jasper” has become commercialized and misused by many sellers. Jasper (from the ancient Greek for “spotted stone”) has a variety of colors, patterns, and textures that make it a very popular gemstone worn in jewelry and sought after by collectors and geologists. The authors recommend the use of the term “dalmatian stone” rather than “dalmatian jasper,” since the material does not meet the gemological definition of jasper. Black spots found in the examined rock’s mass were recognized as arfvedsonite.
It consists predominantly of feldspars (mesoperthite), quartz, alkali amphiboles, and lesser amounts of hematite and epidote. Our research revealed that this gemstone is a peralkaline rock of uncertain provenance. “Dalmatian jasper,” also known as “dalmatian stone,” is a popular decorative gemstone with a unique appearance resembling the spotted coloration of the Dalmatian dog breed. Right: A polished bracelet (1 cm bead diameter) alongside a pendant measuring 3 cm in length.
Left: A rough block-shaped specimen measuring 1.5 × 1.5 × 1 cm. Dalmatian stone samples examined in this study reveal a spotted appearance connected with the presence of alkali amphiboles disseminated through feldspar-quartz matrices. Comprehensive CAD/CAM For Jewelry Certificateįigure 1.
0 kommentar(er)
