Characterization of the Sündikendağı deposit of moganite-rich, blue chalcedony nodules, Mayıslar–Sarıcakaya (Eskişehir), Turkey

Hatipoğlu, Murat; Chamberlain, Steven C.; Kibici, Yaşar

doi:10.1016/j.oregeorev.2013.03.004

Cited by 4 publications

(1 citation statement)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There are many blue chalcedony deposits with economic reserves located in different regions of Turkey. According to Hatipoğlu and Chamberlain (2009) and Hatipoğlu et al (2013), they include: Saricakaya (Eskisehir), the most relevant Turkish blue chalcedony deposit used since the Roman period, Kibriscik (Bolu), Bayat (Afyon), Aliaga and Bergama (Izmir), and Zile (Tokat). Recently, purpleblue agates coming from the Yozgat Province, which is located in the northeast part of central Anatolia, have come onto the gem market (Başıbüyük 2018).…”

Section: Introductionmentioning

confidence: 99%

Atomic and microstructural origin of banded colours in purple-blue variety of agate from Yozgat Province, Turkey

et al. 2022

View full text Add to dashboard Cite

Agates from Yozgat province are appreciated on the gem market for their white and purple-blue banded colours. In this study, we present a detailed investigation aimed at the identification of the atomic and structural origin of this peculiar colouration of chalcedony. X-ray diffraction and Raman spectroscopy revealed the presence of fine grains of quartz and moganite with a preferential accumulation of the latter in the blue bands. Near-infrared diffuse absorption spectra show overtones of hydroxyls vibrations at 1425, 1900, and 2250 nm. In the visible, the broad absorption at about 500 nm, as well as its behaviour at low temperatures, is compatible with the optical activity of iron impurities in quartz matrices, such as that observed in amethysts. Peak intensities and shapes are very similar for spectra collected in blue and white bands. Accordingly, trace-element composition from laser ablation inductively coupled mass spectrometry confirmed that the two regions have similar Fe content. The perceived changes in band colours are indeed originated by differences in microstructural arrangement and size of the grains visualised through scanning electron microscopy. White and blue stripes have grains of about 5 µm and 300 nm in size, respectively, resulting in an accentuated scattering component for the white bands. Therefore, the unique purple-blue shades typical of Yozgat agates are a combination of iron-related colour centres and scattering effect.

show abstract

Section: Introductionmentioning

confidence: 99%