Download AZUL ARAN - Draenert

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Petrographic assignment:
Colouring minerals:
Average hardness:
slab with irregular pattern
Salvador, Silver Blue, Valdaran
Plutonic rock - Plutonite
320 million years (carboniferous)
grey-blue and whiten feldspar, transparent quartz,black biotite, silver muscovite
6-7 (according to Mohs's hardness scale 1-10) / Natural stone
in Aran-valley in the Pyrenees, Spain
Pegmatite is gait-type deposited coarse to giant grain, deposited gait-type form in deep rocks with feldspars,
quartz and some mica. In addition, they often contain rare minerals and precious stones with beautifully
shaped crystals. Pegmatite gaits seldom reach widths of over 10 m thickness in the base rocks. Azul Aran is a
special case, as it shows a relatively uniform structure over a large extent: Blue-grey, very coarse-crystalline
areas of potash feldspar and transparent quartz alternate with also coarse-crystalline white feldspars and
inclusions of up to 5 cm in size, black-grey biotite needles (dark mica). Finely distributed muscovite scales
(light mica) give the rock a silvery shine. Despite its optical advantages, Azul Aran shows two disadvantages:
On the one hand, brown discolouring may occur around the iron-containing biotite and on the other hand, mica
scales continue to brake off during sawing and polishing from not dimensioned plates and bottom plates und
small craters appear.
Pegmatite is interpreted as residual melts, which entered at the start of cooling down into the clefts and gaits
after the granite magma had risen and slowly crystallised there. Due to special geo-chemical circumstances,
'giant crystals' formed from feldspar, quartz and mica. Azul Aran is an exception, as it is an unusually large
deposit of Pegmatite. It is assumed that the residual melt entered in the shape of a hilltop into the lower
portion of the granite magma and made space for itself, as the boundary areas of the granite were melted
again due to the high temperature.
Hint: The close-up view of each stone type shows a relatively true image of the crystalline structure and the
colouring. This is suitable for grained slabs to a limited extend only. In regard to the colour matching, please
take an original sample of the stone from your furniture store as a basis.