Rocks are classified according to their composition and color.

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In geology it is called rock to each one of the diverse solid materials, formed by crystals or grains of one or more minerals, of which the solid part of the Earth and other planetary bodies is made. On Earth the crust is made of rock. The study of rocks is called petrology.

Rocks can be classified according to their properties, such as chemical composition, texture, permeability, among others. In any case, the most used criterion is the origin, that is, the mechanism of its formation. According to this criterion, they are classified as igneous (or magmatic), sedimentary and metamorphic, although a class of alteration rocks can be considered separately, which are sometimes studied among sedimentary rocks.

the aksumite empire was an ancient kingdom located in what is now northern ethiopia from the period of 100 ad to 940 ad. its capital was the city of aksum. the kingdom established itself as one of the 4 great powers at its time, along with persia, rome, and china.

the kingdom was rich in goods like gold, iron, and salt. it established strong commercial ties with the regions governed by rome, egypt, and persia (arabia). aksum was a key location in this commercial network. trade was also facilitated with the introduction of the aksumite currency.