Post by Admin on Sept 25, 2022 12:06:22 GMT -7
Chalcedony is a microcrystalline variety of quartz that has a fibrous morphology. It is most commonly length-fast, implying that the fibers are elongated perpendicular to the c axis of quartz(e.g.Graetsch,1994).
Length-slow chalcedony, composed of fibers elongated parallel to the c-axis (e.g. Miehe et al., 1984), is more rare and has been related to conditions with high alkalinity (eg. Folk &Pittman, 1971; Arbey, 1980; English, 2001; Bustillo 8; Alonso-Zarza, 2007), although this has to be done with caution (Keene, 2006). An alternation of Length-fast and length-slow chalcedony in vug infillings may reflect fluctuations in pore water composition (Summerfield, 1983b).
The tendency of increasing crystal size towards vug centres suggests a declining rate of flow of si|ica—bearing solutions, in response to progressive void infilling and porosity reduction.
Brazil Twinning is caused by iron atoms entering and disrupting the crystal structure.
In Desert Roses, the fibers begin twisting and turn into curly worms and blobs.
Length-slow chalcedony, composed of fibers elongated parallel to the c-axis (e.g. Miehe et al., 1984), is more rare and has been related to conditions with high alkalinity (eg. Folk &Pittman, 1971; Arbey, 1980; English, 2001; Bustillo 8; Alonso-Zarza, 2007), although this has to be done with caution (Keene, 2006). An alternation of Length-fast and length-slow chalcedony in vug infillings may reflect fluctuations in pore water composition (Summerfield, 1983b).
The tendency of increasing crystal size towards vug centres suggests a declining rate of flow of si|ica—bearing solutions, in response to progressive void infilling and porosity reduction.
Brazil Twinning is caused by iron atoms entering and disrupting the crystal structure.
In Desert Roses, the fibers begin twisting and turn into curly worms and blobs.