Heated goethite and natural hematite: Can Raman spectroscopy be used to differentiate them?

Renewable chitin from marine sponge as a thermostable biological template for hydrothermal synthesis of hematite nanospheres using principles of extreme biomimetics

“…Similar phenomenon has been reported for collagen silicification [47], synthesis of collagen/zirconia [48] and calcification of chitin/chitosan hydrogels [49]. Ma et al [50] have also confirmed similar influence of polysaccharides (like cellulose) on morphology and crystallinity of in vitro hydrothermally prepared iron oxides.…”

“…Several studies regarding the use of biological templates in hydrothermal synthesis of hematite have been performed. Mostly these studies are based on (i) hydrothermal carbonization of the biological molecule and deposition of hematite on the carbon template [66], or (ii) utilization of the biopolymer as a soft driving structure for hydrothermal growth of hematite, and then subsequent removal of the template by sintering [50]. From the perspective of preparation of hybrid organic-inorganic (biopolymerhematite) structures, hydrothermal technology is still poorly investigated.…”

Composition of a floor from an Upper Paleolithic skeletal grave – A case from Dolni Vestonice (Moravia, Czechia, Central Europe)

“…Presumably heated powders of "ochre" were identified in the material from Dolní Věstonice discussed above, where Raman spectroscopy demonstrates hematite spectrum of clearly deformed crystalline structure. Such structure is characteristic of both weathered and heated rocks (de Faria, Lopes 2007); in the first case only for those which contain quite large amounts of primary hematite (Trąbska et al, unpublished). The heating could not have been too intensive and long lasting because this (for example, 800ºC for 12h) completely deforms the mineral structure (see above), even if the primary hematite was highly structured (de Faria, Lopes 2007).…”

“…Such structure is characteristic of both weathered and heated rocks (de Faria, Lopes 2007); in the first case only for those which contain quite large amounts of primary hematite (Trąbska et al, unpublished). The heating could not have been too intensive and long lasting because this (for example, 800ºC for 12h) completely deforms the mineral structure (see above), even if the primary hematite was highly structured (de Faria, Lopes 2007). The occurrence of minerals formed at high temperatures (e.g.…”

“…Taką strukturę zaobserwowano dla hematytów zwietrzałych lub przegrzanych (de Faria, Lopes 2007). W odniesieniu do proszków ze stanowiska Dolní Věstonice przegrzewanie nie mogło być zbyt intensywne ani długo trwające: z naszych badań wynika, że proces trwający 12h w temperaturze 800 o C zupełnie czerwone proszki żelaziste jako źródło informacji archeologicznej niszczy strukturę hematytu (por.…”