AGNAOU GATE
The Minero-Petrographic Analysis

Sample PA 1:
green rock (of recent substitution/restoration ?)

the rock shows a highly linear structure formed by very thin levels of calcite and phillosilicates alternating with others of very fine-grained quartz. The main minerals are:
- Quartz, in single and polycrystalline individuals.
- Sericite/muscovite in thin levels or trains. The largest needles are often associated with chlorite forming characteristic sandwiches (Fig. a).
- Calcite, which is much less abundant than the previous components and forms single individuals or, more rarely, associations with sericite.
- Opaque minerals of irregular shapes (Figs. b-c) or very dispersed /concentrated in fine particles are quite abundant, sometimes associated with small limonitic masses.

The only accessory mineral observed is an epidote in tiny crystals with a green-brown pleochroism and crossed extinction.

The rock may be classified as a metamorphised siltstone formed in the green-shist facies.

Sometimes a system of iso-parallel micro-fissures due to deterioration can be seen close to the external surface of the sample (Fig. d).

a)


b)


c)


d)

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