Visit Al-Zaytuna Mosque and discover the fascinating rock types of the building!

The mosque is made of different rock types which have been combined to make a fascinating, religious building in the Medina of Tunis. Get some information about the stones:

MARBLE

Marble is a metamorphic rock that forms from the metamorphism of limestone or dolomite rocks. Metamorphism occurs when existing rocks are subjected to high temperature and pressure conditions deep within the Earth's crust, causing their mineral composition and texture to change.

Marble is primarily composed of the mineral calcite, which is the crystalline form of calcium carbonate (CaCO3). During metamorphism, the calcite crystals in limestone recrystallize and grow larger, resulting in the distinctive coarse-grained texture and characteristic veining patterns seen in marble.

The color of marble can vary widely depending on the impurities present during its formation. Pure marble is white, but impurities such as clay minerals, iron oxides, organic material, and other minerals can impart hues of gray, green, pink, blue, or yellow.

Marble is prized for its beauty and has been used for centuries in sculpture, architecture, and as a decorative building material due to its smooth texture, luster, and ability to take a high polish. Its durability and resistance to heat make it suitable for a wide range of applications, from countertops and flooring to monuments and artwork.

Source: based on https://en.wikipedia.org/wiki/Marble

SANDSTONE

Sandstone is a sedimentary rock composed primarily of sand-sized mineral particles or rock fragments, usually quartz, cemented together by various minerals such as silica, calcite, or iron oxide. It forms through the process of sedimentation, where sand grains accumulate and are compacted and cemented over time.

The grains in sandstone are typically quartz, although they can also include other minerals such as feldspar, mica, and lithic fragments. The mineral composition of sandstone can vary depending on the source material and the depositional environment.

Sandstone is characterized by its gritty texture and often displays distinct bedding planes, reflecting the layers of sedimentary deposition. These layers can vary in thickness and composition, indicating changes in environmental conditions over time.

The color of sandstone can range from white to yellow, red, brown, or even purple, depending on the presence of iron oxide or other pigments. It can also exhibit various patterns and structures, including cross-bedding, ripple marks, and fossilized remains.

Sandstone is a versatile building material and has been used for millennia in construction, architecture, and sculpture. Its durability, ease of carving, and availability make it a popular choice for building facades, walls, flooring, and decorative elements. Sandstone's porous nature also makes it suitable for use as a reservoir rock for oil and gas extraction.

Source: based on https://en.wikipedia.org/wiki/Sandstone

LIMESTONE

Limestone is a sedimentary rock primarily composed of calcium carbonate (CaCO3) derived from the shells and skeletons of marine organisms such as coral, foraminifera, and mollusks. It forms through the process of biochemical sedimentation, where the accumulation of calcium carbonate-rich remains undergo compaction and cementation over time.

The texture of limestone can vary from fine-grained to coarse-grained, depending on factors such as the size and composition of the original organic material, as well as the degree of compaction and recrystallization. Some limestone varieties may contain fossilized remains, such as shells or other marine organisms, which are often visible in the rock.

Limestone is typically light in color, ranging from white to gray, yellow, brown, or even black, depending on impurities present during formation. Iron oxides, organic matter, and other minerals can impart various hues to limestone. Limestone often exhibits bedding planes and may display features such as cross-bedding, ripple marks, and fossilized structures, reflecting the depositional environment and processes involved in its formation.

Due to its abundance and versatility, limestone has been used for centuries as a building material, particularly in architecture and construction. Its durability, workability, and aesthetic appeal make it suitable for a wide range of applications, including building facades, flooring, countertops, monuments, and sculptures. Additionally, limestone is used in industries such as cement manufacturing, agriculture (as a soil conditioner), and in the production of lime for various industrial processes.

Source: based on https://en.wikipedia.org/wiki/Limestone

THE EARTHCACHE

On the façade of the Al-Zaytuna Mosque you can find all three types of rocks. The speciality of this location is the combination of all three stones. This is hardly else found in Tunis or even in the Medina of Tunis in this epoch. One has to consider that the Mosque has been built in the year 732. Sandstone and Limestone are native to Tunisia. However, Marble is not. During the construction of the mosque about 1,300 years ago, the caliph imported marble from Greece.

Please move to the location of the earthcache and watch:

• • The columns
  • The archs from column to column
  • The wall around the brown front door

For logging this earthcache, please answer the following questions:

1. Please describe the three above mentioned building elements regarding colour, texture, hard-/smoothness.
2. Therefore tell me which of the elements is made of marble, sandstone and limestone?
3. Why did the creators of the Mosque choose this rock types for the three elements?
4. To prove that you were at the location: On the white wall behind you, you find a map of the Medina of Tunis, a post box and what else?
5. A picture of the location with you, your GPS receiver or something showing your Geocaching nickname is mandatory.

You do not need to wait for my logging permission. You can log after sending the answers. Logs which do not fulfil the requirements, will be deleted without prior notice. Please do not forget the picture!

Have fun exploring the fascinating Medina of Tunis!