| Abstract | Gemološki materijali su minerali ili materijali organskog podrijetla koji se proučavaju unutar gemologije, kako bi se identificirali, klasificirali i vrednovali. Ti se materijali koriste u različite svrhe, za uljepšavanje, ukrašavanje, dekoriranje te u umjetnosti. U ovom se radu obrađuje 16 uzoraka turmalina, kako bi im se odredila gemološka kvaliteta i na koji način ih je prikladno brusiti. Četiri uzorka su obrađena, dok su ostali neobrađeni. Na prvi pogled uzorci se razlikuju po boji, no imaju zajedničke karakteristike poput habitusa, zonalnog obojenja, prisutnosti pleokroizma, prutanja paralelnog izduljenju, prozirnost, staklast sjaj te vanjska i unutrašnja oštećenja. Kako bi se odredio prikladan način za njihovu obradu, tijekom određivanja gemološke kvalitete ovih uzoraka obraćala se pažnja na prethodno navedene karakteristike. Stoga je na odabranim uzorcima korišteno 5 različitih metoda ispitivanja fizičkih i optičkih svojstava - vizualni pregled golim okom i lupom s povećanjem 10x, i pregled gemološkim instrumentima polariskopom i refraktometrom. Korištena je i metoda FT-IR spektroskopije, kojom se odredilo o kojim vrstama turmalina se radi: 10 uzoraka je određeno kao elbait, jedan je određen kao fluoro-elbait ili dravit, jedan kao dravit ili uvit, jedan kao fluoro-elbait i elbait ili fluoro-uvit i jedan kao fluoro-elbait, a za 2 uzorka nije bilo moguće dobiti rezultate o vrsti turmalina. U konačnici je određena kvaliteta obrade kod 4 rezana uzorka turmalina: dva su vrlo dobre, jedan je dobre i jedan je osrednje kvalitete obrade. Određena je i kvaliteta neobrađenih uzoraka i način orijentacije za njihovo brušenje: 7 uzoraka je potrebno orijentirati tako da im stolna ploha bude paralelna c osi, a stolna ploha 5 uzoraka se može orijentirati ili paralelno ili okomito osi c. K tome, je određen prikladan stil reza: stepeničasti rez za 6 uzoraka, stepeničasti ili miješani stil za 3 uzorka i rez u kabošon za 3 uzorka. |
| Abstract (english) | Gemological materials are minerals or materials of organic origin that are studied within gemology to be identified, classified, and evaluated. These materials are used for various purposes, such as embellishment, decoration, ornamentation, and in art. This work addresses 16 tourmaline samples to determine their gemological quality and the appropriate way to cut and polish them. Four samples are faceted, while the rest is in their rough state. At first glance, the samples differ in color, but they share common characteristics such as habit, zonal coloring, the presence of pleochroism, striations parallel to elongation, transparency, glassy luster, as well as external and internal damage. In order to establish an appropriate processing method, attention was given to the aforementioned characteristics during the determination of the gemological quality of these samples. As a result, five different methods were employed to examine their physical and optical properties - visual inspection with the naked eye and a 10x loupe, and examination using gemological instruments like a polariscope and refractometer. FT-IR spectroscopy method was also used in order to identify the tourmaline species: 10 samples were determined as elbaite, one as fluoro-elbaite or dravite, one as dravite or uvite, one as fluoro-elbaite and elbaite or fluoro-uvite, one as fluoro-elbaite, and for 2 samples, it wasn't possible to obtain results regarding the species of tourmaline. In conclusion, the processing quality of 4 faceted tourmaline samples was determined: two were of very good quality, one was of good quality, and one was of moderate processing quality. The quality of untreated samples was determined, along with the orientation for their cutting: 7 samples need to be oriented so that their table facet is parallel to the c-axis, and the table facet of 5 samples can be oriented either parallel or perpendicular to the c-axis. Moreover, a suitable cutting style was determined: step cut for 6 samples, step cut or mixed cut for 3 samples, and cabochon cut for 3 samples. |
