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(FesO-O and rutile (TiO:). The thermal decomposition of pyrite and tłie dihydroxylation of amorphous iron phases not detected by XRD ni the raw samples might be responsible for the apparition of hematite and magnetite. The formation of anhydrite rriay be attributed to the contact between calcium rich minerals (ex. calcite) and sulfiir oxide gases caused by the decomposition of sulphide minerals (ex. pyrite). Tlie disappearance of muscovite minerals may be responsible of the apparition of spinel phase (WF and RE, 1951). It is reported tliat muscovite starts to decompose into vitreous phase and into mullite starting from 800^:'C (Cultrone et al., 2001). Nevertheless, it is noted that the mineralogical composition of all stndied samples was mostly tlie same with some minor differences m tenns of ąuantity. As a conclusion, the physical and mechanical properties difference among the studied samples was highly mfluenced by the vitreous phase content.

hB- 1C20    MWR-1020    CMT-1020

180 160 140 Co 120

ON

Z

) 100

■

$

i 80 “i

: 60 40 20 0

Anhydrite Magnetite Hematite Rutile Spinel

Figurę 7.10

Quantification of ciystallme phase minerals in fired CMWR, TCMT and SliB samples.