Detail Slab
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Portoro Silver

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.


The main mineral calcite exhibits traces of organic substances (bitumen) which cause the gray and black coloring. That kind of limestone was generated by deposits of calcereous ooze on the sea bed.


Limestone consists of sediments of chemically precipitated chalk, mostly under the influence of organisms which form calcareous skeletons or calcareous shells. The lime sludge compacts to solid limestone. In the case of the Portoro Silver, a polished surface is possible because of highly compact layers of calcareous elements. Over millions of years, fractarures generated by plate-tectonic movements in the earth’s crust, subsequently were filled by crystalline white calcite. 

Hardness Soft Stone
Structure Type Slab with Irregular Pattern
Synonyms Port Black, Silver Dragon
Group Sediment rock
Petrographic Assignment Limestone
Age unknowm
Colouring Minerals Black bitumen embedded in white calcite, light gray crystalline calcite
Average Hardness 3 (according to Mohs’s hardness scale 1-10)
Deposit China