Abstract

Natural stone building materials have been prized by many civilizations in the building of tombs, homes, temples and other monuments. The exceptional colors, hardness, and many other physical characteristics added to the desirability of the various stones. The use of rare and beautiful stone was especially evident in ancient Greek and Egyptian monuments and statues. The ancients took much trouble to seek out the most beautiful of rocks to glorify what they considered deserving of praise or reverence. This paper will serve as an overview of the history of building materials in antiquity, as well as a survey of geologic properties and settings for the rocks chosen by the ancient Greeks and Egyptians.

Cultural Significance of Monuments in Greek and Egyptian Civilizations

In order to gain a better understanding of the cultures that spawned an ongoing legacy of grandiose sculpture, architecture and other artistry, one must first understand the mindset of the civilizations from whence they were created.

The Greek civilization at the time of the major monuments (Acropolis, Agora, Delphi) in the 4^th and 5^th centuries BC was enveloped in an intellectual renaissance led by the great philosophers of the time. To promote their advanced intellectual society as well as to worship their gods, the Greeks built beautiful monuments of the finest marble. The Parthenon is a prime example of such a monument, built to exemplify perfection. This monument was constructed to worship Athena and to be a symbol of strength and excellence of the Greek Empire under Pericles’ rule.

The Egyptian Empire built monuments over an extremely long period of time, beginning in Dynasty I (3200-2980 BC) with the brick tombs and increasing in magnificence with the pyramids in the 5^th dynasty (2565-2420 BC). This trend continued throughout the successive dynastic periods until the civilization was occupied by the Persians and the Romans around 500 BC (Smith, 1990). The motivation behind the creation of the many monuments was largely rooted in faith. The elaborate polytheistic religion of the Egyptians permeated every aspect of their daily life. Natural phenomenon such as the flooding of the Nile and the yearly/daily astronomical cycles of heavenly bodies intrigued and inspired the Egyptians to create monuments and artwork in adoration for such seemingly mystical happenings (Ben-Tor, 1997).

These beliefs were incorporated with the prestige of the ruling king or queen, who occasionally sparked a cult following or was esteemed to a point where the line between god and man began to blur (Grimal, 1994). These rulers then considered it of extreme importance, if the means were there, to erect great monuments to revere their personal gods.

For both the Greeks and the Egyptians, the great importance placed on beautiful sculptures and monuments required only the finest materials to exult the civilization and the religion. It was this desire that fueled the search for the now legendary marbles, granites, porphyries and other stones that are associated with such structures. Obtaining suitable materials was not an easy task and exemplified the importance these civilizations placed upon worship.

Obtaining and Quarrying Building and Sculpting Stones

The constraints of geometry, trigonometry, manual labor and the simplest of devices limited the technology of the ancient Egyptians and Greeks. The determination of these civilizations was the fuel to create monuments that have withstood the wear and tear of time.

The basic quarrying methods for both the Greek and Egyptian civilizations were performed with knowledge of the natural properties such as the hardness of a rock and the natural faults and spacing of veins (Fant, 1998). The ancient quarrymen had to estimate how a rock would fissure if hit in a certain location as well as choose sections for quarrying that exhibited desirable characteristics within the stone such as purity, strength and beauty. Even with the geologic expertise of the quarrymen, in most cases, about two-thirds of the quarried stone would be discarded later (Korres, 2000).

The blocks of stone were extracted using wedges and hammers. Extra material was removed from the block to eliminate any small fissures and other undesirable characteristics of the stone. Each roughly shaped block was then moved from the quarry to a wagon or a ship that transported the block to the site of stoneworking, where the block was shaped.

Egyptian Methods

The Egyptians, being a more established civilization than the Greeks at 3000 BCE, developed quarrying techniques that generally predated and possibly inspired the Greek methods of quarrying. At the beginning of Egypt’s long history of quarrying, the tools used were primitive copper implements that were only able to extract softer stones such as sandstone and limestone. These were much easier to fissure than igneous granite or metamorphosed quartzite. As the civilization advanced, the tools were formed from bronze and then iron. These tools allowed the Egyptians to exploit the harder, more desirable stones such as granite and quartzite. Eventually, hammers made of dolerite were used to create larger trenches and holes necessary for the quarrying process (Fant, 1988). Another technique that may have been used to carve the harder blocks of granite and quarzite from the surrounding rock was the practice of thermal shock. This method consisted of heating the rock and then dousing it with water to weaken the stone allowing the quarrymen to fissure the rock (Waelkens and Herz, 1988).

Greek Methods

The Greeks preferred marble as their major building stone, most likely because of its wide availability and exceptional beauty. Greek marble was quarried from many different sites, all with differing characteristics in the marble. These varieties of stone will be discussed later in this paper. Techniques of quarrying, as mentioned before, may have been derived from the methodologies of the Egyptians. There are a few differences that are attributed to advancements in the field of stone working. For example, the Greeks favored picks for their main implement of quarrying (Fant, 102).

The large amount of manpower and time involved in the quarrying endeavors illustrated the great accomplishment of these civilizations when monuments such as the Parthenon and Karnak were erected. The immense amount of work, rarity of the stones and discriminating tastes of the rulers placed much value on these building materials.

Geologic Attributes of Greek Marbles

It is difficult to characterize all the Greek marbles with one sweeping description, so two specific marbles will be described according to their appearance, hardness, composition, location and geologic significance.

Marble is essentially limestone that has been subjected to heat and pressure, turning it into a harder, more compact stone. The mechanism for this metamorphism can be recrystallization due to regional, contact or dynamic metamorphism (Mottana et. al., 1978). The chemical composition of marble is typically calcite (CaCO₃) with minor traces of dolomite (MgCO₃). Most marbles are white or off-white in color, however the stone can occur in more exotic hues due to minor impurities within the stone. Specific varieties of marble can be identified by the petrographic character of the stone as well as its isotopic signature (Waelkens and Herz, 1988).

Pentelic Marble is the variety that makes up most of the monuments on the Acropolis (Figure 1). The quarry is located on Mount Pentelikon, outside of Athens (Waelkens and Herz, 1988). This variety of marble was not the purest of the Greek stones; however, it was used because its geographic location was closest to the Acropolis, making it easier to transport to the site of the monument.

Figure 1:Example of Pentelic Marble

Picture from: http://home01.wxs.nl/~kardun/greek-marble.htm

This stone has a homeoblastic texture, meaning the grain size was very consistent, and the grain boundaries are a combination of straight and gently curving. The average grain size is 0.2 mm in diameter. Some of the minor impurities within the stone include quartz (SiO₂), dolomite (MgCO₃), muscovite (KAl₂(AlSi₃)O₁₀(OH)₂), and iron ore (Waelkens, 267).

Parian Marble is another significant stone that was used in antiquity (Figure 2). This stone originates on the Greek island of Paros and was used in many sculptures and temples. This stone was highly prized for its crisp white color and larger grain size. The quarry is located on the small island of Paros, and its somewhat isolated, distant location limited the use of Parian marble in large-scale endeavors. It is for this reason that most of the artifacts that are composed of Parian marble are small but beautiful statues.

Figure 2: Example of Parian Marble

Picture from: http://www.greekmarble.com/area/aegean/cyclades/paros/ashwhite/home.htm

The marble is purer than the Pentelic marble from mainland Greece. The Parian quarry varies in composition and texture within the site, with some layers exhibiting homeoblastic texture and others exhibiting heteroblastic texture. The average size of grains ranges from 0.1-0.4mm, the larger grains giving the marble a grainier look than the Pentelic stone. Pentelic marble is sometimes prone to shearing and strain (Waelkens and Herz, 1988).

Impurities in the stone include quartz and muscovite in minute quantities. Trace amounts of iron ore, serpentine, tremolite, sphene, rutile and zircon are also found in the presence of muscovite (Waelkens and Herz, 1988). The occurrence of tremolite and serpentine may be indicative of contact metamorphism in the creation of this marble since these two minerals are associated with the contact metamorphism of carbonate rocks (Waelkens and Herz, 1988).

Geologic Attributes of Significant Egyptian Quarried Stones

Egypt contains a wide variety of ornamental building stones that were utilized for various monuments, sculptures and structures. Among these stones, there are several that epitomize the Egyptian ambition in building monuments for their gods and pharaohs. Granite and limestone are certainly among the most plentiful resources in Egypt, but rarer stones such as the purple-black “imperial” porphyry were also important in the endeavors of the civilization.

Granite is an intrusive volcanic rock that can vary widely in composition, texture and color. The general chemistry and appearance of granite is generally consistent. Granites are always composed of a combination of quartz, orthoclase feldspar, microcline feldspar, plagioclase, and biotite (a kind of mica). Magnetite, ilmenite, other varieties of mica, hornblende, pyroxene and garnet can also be found as minor minerals in granite, depending on the source magma from which it forms (Mottana, 1978).

The setting of granite formation is commonly associated with a batholith or pluton, which is a large intrusion of magma that cools slowly under other layers of rock in the Earth’s crust. The slow cooling results in large crystal size in the granites. Sometimes, in the late stages of cooling, the granite is differentiated with small grained pegmatite veins and aplite inclusions (Figure 3). The typical pink color of Egyptian granite can be attributed to the abundance of potassic feldspar (microcline and orthoclase). The potassic feldspar crystals are sometimes so large they are referred to as porphyritic (Hume, 1934).

Egyptian granites are prevalent in many locations from the granites of the Sinai Peninsula, to the famous Aswan granites. The stone has been referred to as “rose syenite” and “Oriental granite” gaining these nicknames due to its striking pink color (Hume, 1934). The granites from Aswan were highly prized and transported via the Nile to

many important sites such as Karnak, Luxor Temple, Giza and Edfu. In particular, the

Figure 3: Pegmatite Veins in Egyptian Granite, Picture from Isis Temple in Nile Delta

Aswan granite was used for obelisks that are prominently on display at Karnak. These huge (as large as 108 feet tall) structures were quarried out of Aswan sites in one piece and transported by a large boat to the temple site. Aswan granite was also used for sculpture as it withstands the tests of time far better than the weatherable limestone and marble.

Limestone was the material of choice for the Sphinx and the pyramids at Giza. Limestone is a sedimentary rock composed largely of calcite. The hardness and susceptibility to weathering is determined by its original depositional conditions when the rock was being deposited. Fossils are commonly preserved in this rock since the original environment is that of shallow marine shelves that harbor many organisms with body parts made of calcite or similar materials. As these animals die, their remains accumulate on the floor of the shelf, where they are buried and lithified. The regional conditions determine the amount of clay and mud that change the appearance and integrity of the limestone as well as its purity (amount of CaCO₃) (Mottana et. al., 1978).

Limestone also can vary stratigraphically at the same location. The depositional environment of carbonate shelves wax and wane with changes in water depth. These water depth changes alter the composition of the limestone, with either more or less carbonate material. These variations can either fortify or weaken the integrity of the stone.

The most famous Egyptian structures, the Sphinx and the pyramids at Giza were constructed from different varieties of limestone. The Sphinx was constructed from 50-million-year-old limestone found in situ, and the stratigraphy can be easily observed on the monument with the head and neck being a separate overlying member of the series of limestones making up the monument (Figure 4). The lower strata are composed of cyclic micritic limestone, characteristic of a lagoon with alternating resistant and less resistant layers (Lehner, website). The strata are a part of a local series of gentle anticlines that result in a slight angle of the bedding planes (Gauri, 1988).

Figure 4: Schematic Cross Section of the Sphinx indicating beds of limestone. (Gauri, 1988)

The pyramids are also made of limestone, but the limestone is derived from a different source. The large volume of pyramid rock was brought from local quarries, mostly from the Giza Plateau itself. Most of this limestone was rich in nummulites, which are flat, disk-shaped fossils that have calcareous shells (Lehner, Website). There was also purer limestone brought from Tura, which is a location across the Nile from the Giza Plateau (Smith, 1990). This special limestone was used as a casing material to add to the resplendency of the monuments. In addition, the pyramids were once entirely cased in granite from Aswan. The Aswan granite was also used in some of the chambers as well as more exotic materials such as alabaster, diorite, and basalt.

Imperial porphyry is one of the more exotic stones used in Egyptian architecture and sculpture. Porphyry is a variety of intrusive igneous rock formed by slowly rising magma in the crust of the earth. As the magma rises, large phenocrysts, or differentiated crystals form while the rest of the rock remains molten. The rock will eventually “erupt” to the surface where the rest of the magma will quench quickly forming a fine-grained matrix of crystals around the large phenochrysts (Thompson and Turk, 1997).

The intrusive conditions required to form porphyry restrict the volume of quarryable material to dikes and small intrusive plutons. For this reason, it was not plausible for entire monuments to be made out of imperial porphyry. Instead, statues were made of this material. The rich exotic colors of the stone were highly desirable for such works. Porphyry was especially prized by Roman emperors later in time near the close of the Egyptian empire (Hume, 1934).

The chemical composition of porphyry is highly variable based on the composition of the parent magma. Commonly, the phenocrysts are felsic in composition with a matrix of several minerals including quartz and feldspar (Hume, 1934). Imperial porphyry has a characteristic purple hue (Figure 5) that is attributed to the presence of hematite in the rock matrix (Hume, 1934). The hardness of the rock is over twice that of Aswan granite, presumably due to its smaller crystal size. The quarrying locations for this exotic stone are remote and harsh. It is for this reason that the stone is even more prized for its rarity and novelty.

Figure 5: Sketch of Imperial Porphyry (Hume, 1934, Plate XCV)

Conclusions

The use of beautiful natural stone in ancient monuments was a common practice in both Greek and Egyptian civilizations. The extremely large amount of work involved in quarrying, transporting, sculpting and constructing monuments illustrates the great importance the Greek and Egyptian rulers placed upon revering their gods, glorifying their rulers, and displaying the power of their empires.

Essential to the endeavor of creating such monuments is the geologic setting of both of these countries. Although both civilizations transported materials from extremely far distances to be used in building and sculpting, transportation was a limitation when constructing large-scale monuments such as the pyramids and the Acropolis. Each of those monuments required a huge volume of stone.

This demand for building materials was largely satisfied by local rock, quarried out of sedimentary sequences, plutons and intrusive dikes. Limestone, granite, porphyry and marble exist in many other areas of the world, but it is difficult to find examples that are more spectacular than those located in Greece and Egypt. There is no question that the richness of architectural materials and sculpture in both countries was aided by these resources. The beauty of these civilizations’ creations therefore is dependent on local and regional geology, for many areas of the world would not be able to create such spectacular monuments due to lack of suitable materials.