THE COMPOSITION OF KARYSTIAN MARBLE
Rock which is known as marble consists largely of limestone which has undergone certain transformation and metamorphism. This can be due to either chemical or physical conditions. Metamorphism is ‘the response of the buried rock to changes of pressure and temperature as well as to chemical variations of its make up’. There are several different types of metamorphism. It can be through the effects of heat due to volcanic magma, through breaking up or overlapping of the rock which can cause crushing or grinding up, or hydrothermal metamorphism caused by gases or high temperature solutions.
These different processes cause varying formations and structures of the rock to occur. They also produce ‘trace elements which appear in the crystalline sections and can indicate the area of the formation of the different rocks, as these elements vary according to the factors which cause the metamorphism’.13
Besides the main ingredient, limestone, Karystian marble also contains one or both of the minerals, muscovite and chlorite. ‘These appear either on their own, wedged between the limestone grains or as lens-shaped concentrations. Muscovite appears silvery white to light green and chlorite bright to dark green. It is to these two minerals, and particularly chlorite, that Karystian marble owes its green tones.’ Quartz is a common component, ‘formed of clear grains of different sizes’. Plagioclase is present in small grains and epidot, ‘an important essential in the green layers’.
The essential mineralogical components, according to their density and proportion give the stone different tones: light green, grey green, sapphire green and ash white to dark grey. The ash tones are due on the one hand to the flint minerals, but on the other hand, more to the dust which is dispersed in the limestone grain which appears to consist of carbon properties and the oxide Fe and Mn. This can give to the marble a dark ash to almost black colour.14
In his book which contains a whole chapter on the cipollino marble, Lazzarini describes the mineral-petrographical analysis of Karystian cipollino, taken from about 100 specimens from 33 of the biggest quarries in the three main districts where the marble was quarried in Roman times, that is Styra, Marmari and Karystos.15 According to these surveys the cipollino can be described as an impure marble with chlorite (green variety) and graphite (grey variety). The essential minerals, which are contained in the marble, are listed in decreasing order of quantity, as calcite (crystalline calcium carbonate), the most abundant with more than 70 %; quartz, varying between 2-12%; plagioclase from 1-10%; muscovite, colourless or greenish, varying between 2-16% and chlorite also greenish (see Figure 37 of Lazzarini, 2007).
Lazzarini also describes the make up of the Karystian marble, breaking it down into its various mineral elements. He provides a table of these, according to the three main districts already mentioned, Styra (settentrionale), Marmari (centrale) and Karystos (Meridionale). The table shows the composition to be of nine mineral elements and 13 trace elements. The former includes silicon, (a non-metallic element occurring widely in silica and silicates, the largest in quantity), aluminium, iron, magnesium, potassium, sodium, titanium, manganese, phosphorus. The latter includes trace elements, in descending order of amounts present, of barium, chromium, copper, neon, zinc, vanadium, rubidium, cobalt, zirconium; larithanium, cerium and ytirium (measured only in specimen from the Styra area) and lead (measured only in specimen from the Karystos and Marmari districts). The amounts vary slightly according to the three different areas.
For those readers who need more specific details the table can be found on p. 193 of Lazzarini’s book. Further detailed scientific information can be found in pages 193 - 203.16
13 Lambraki, A., Le Cipolin de la Karystie, Contribution a l’Etude des Marbres de la Grèce Exploités aux Epoques Romaines et Paléochrétiennes, Revue Archéologique, 1978, p. 33-34: also note 11.
14 Papageorgakis. I, Ta Achaia latomeia tou Karistou Marmarou, Praktika tis Akademias Athinon, XXXII, 1964, pp.272-4.
15 The subject of the two degree thesis (Ginetti 1992-1993 and Vizzini 1992-1993) followed by a general synthesis (Lazzarini et alii). Quoted in L. Lazzarini, Poikoloi Lithoi, versiculores maculae I marmi colorati della Grecia antica. Storia, uso, diffusione, cave, geologia etc. Roma, 200, Chapter 12, p. 192.