Here are some extracts from the book The Myth of the Andalusian Paradise by Darío Fernández-Morera, which I have written about before (here and here) and will discuss more in future. Listen to an interview with the author above.
The price of a slave depended on his or her race, sex, age, and abilities. White slaves, especially blond ones, often captured in raids of Christian lands, were the most prized. In the year 912, during the Islamic Golden Age of the Umayyad Caliphate of Córdoba, the price for a male black slave was 200 dirhems [coins] of silver. A black girl from Nubia went for 300 dinars of gold. A white girl without education cost 1,000 dinars of gold. A white girl with singing abilities cost 14,000 dinars. In Abd al-Rahman III’s court there were 3,750 slaves, his harem had 6,300 women, and his army included 13,750 slave warriors. A document from the twelfth century tells of the tricks used by sellers of slaves in the Muslim slave markets: merchants would put ointments on slave girls of a darker complexion to whiten their faces; brunettes were placed for four hours in a solution to make them blond (“golden”); ointments were placed on the face and body of black slaves to make them “prettier.”
... Ibn Hazm, himself of European (Spanish) Christian origin, wrote that most Abbasid rulers in the Middle East and all Umayyad rulers in al-Andalus had sexual slave mothers. Many of these mothers were of Caucasian origin. The Arab chronicler Ibn al-Qutiyya, himself of European (Visigoth) Christian descent, affirmed that the descendants of Sarah “The Goth,” a Christian sexual slave, were more illustrious and prestigious within the Andalusian Islamic community than the children her Muslim husband had with other women (in Islamic law, children of Muslim men and non-Muslim women must be brought up as Muslims).
As Arabist Celia del Moral observes, the Umayyads particularly valued blond or red-haired Franc and Galician women as sexual slaves. Indeed, the physical appearance of several Spanish Muslim princes betrayed their descent from Caucasian slave mothers. The Middle East–born founder of the Umayyad dynasty in Spain, Abd al-Rahman I (reigned 755–788), was blond; Hisham I (reigned 788–796) had very white skin and reddish hair; Muhammad I (reigned 852–886) had a pink face; Abd Allah b. Muhammad (reigned 888–912) had white skin, a pink face, blue eyes, and blond hair; Caliph Abd al-Rahman III (reigned 912–961) had white skin, a pink face, and blue eyes, and he tinted his blond hair black to appear more “Arabic” to his subjects; Caliph Hakam al-Mostancir II (reigned 961–976) had reddish hair; and Caliph Hisham II (reigned since 976 variously as a puppet until his assassination in 1013), the last Umayyad ruler, and the son of a Basque sexual slave, a “skilled singer [who] exerted over [his father] great influence,” was blond, with blue eyes and a reddish beard. Abd al-Rahman V al-Mustazhir (assassinated in Córdoba in 1024), who reigned briefly after the death of Almanzor, was blond, and the son of a sexual slave. The founder of the presumably “Arab” dynasty of the Nasrids of Granada, Muhammad b. Nasr (d. 1273), was called “The Red One” (al-Hamar) because of his red beard. Initially, the invaders of al-Andalus were mostly men. Therefore, as Arabic sources indicate, the practice of having children with Spanish Christian women probably began when the son of Musa took as one of his several wives Queen Egilo (or Egilona), widow of the Visigoth king Rodrigo. The European presence in the lineage of Muslim rulers did not stop with the arrival of the Berber Almohads: the Almohad caliph Abu Yusuf Yaqub b. Yaqub b. Abd al-Mumin b. Ali (d. 1198) was the son of a Christian sexual slave girl. Similarly, we know that one of the kings of the taifa kingdom of Granada, Muhammad Ibn Yusuf Nasr (d. 1310) took as one of his wives the captured female Christian ruler of the city of Bedmar, María Jiménez, and had from her several children.
The Spanish Arabist Julián Ribera calculated that, as a result of this sexual intercourse with Caucasian Christian girls, each generation of Umayyad rulers saw its genetic “Arab” component reduced by half, so that the last Umayyad, Hisham II (976–1013), would have had approximately 0.09 percent of “Arabic” genetic makeup. Ribera concluded that already by their second generation Umayyad rulers in al-Andalus had far more European than “Arab” genes; that a similar process of geometrically increased mating between Muslims and native Spanish Christian women or their eventually Muslim female descendants must have diluted dramatically the non-European genetic makeup of the general population of al-Andalus; and that this European Christian factor, with its presumably greater love of individual liberty and regard for the individual human being as opposed to the group, contributed to the again presumably greater “freedom” women enjoyed in Islamic Spain as opposed to other regions of the umma. Whatever one may think of Ribera’s imaginative last conclusion in view of what we now know about the actual condition of Muslim women in Islamic Spain, it is not unlikely that the process he describes would have influenced al-Andalus culturally and socially. Writing in the fourteenth century, the historian Ibn al-Khatib described the inhabitants of Granada as “white skinned.”
The Arabist Felipe Maíllo Salgado has pointed out that modern genetic studies show that the genetic presence of populations from the Middle East and Berber North Africa in the present-day Spanish population is minimal.
Such was the cultural impact on the Islamic Middle Ages of Caucasian sexual slaves from Christian lands that the Turkish word kiz, meaning “girl,” “slave girl,” and “sexual slave girl” (or “concubine”) came to mean also “Christian woman” in Islamic usage.
Analogously, the Arabic word sakaliba (probably derived from the Greek Σλάβος or “Slav”), referring to blond or red-haired peoples, came to designate the child or adult slaves from the eastern and northern European lands, who played a key role in the armies and politics of Muslim states. The tenth-century historian and geographer Ibn Hawqal wrote that in Spain the name sakaliba, as well as “Slavs,” was given to all the white slaves of foreign origin, not only from northern and eastern Europe but also from Christian Galicia and northern Spain, Lombardy, the land of the Franks, and Calabria, who populated the palaces, harems, and the armies, especially the body guards, of the Andalusian rulers. As Mohammed Meouak, professor of Islamic civilizations at the University of Cadiz, points out, in Umayyad Córdoba these Islamized white slaves made up most of the administrative personnel in the Umayyad palaces and courts. As freedmen, some of these “Slavs” seized power and became kings of taifa kingdoms after the disintegration of the Caliphate of Córdoba.
The impact of Caucasian sexual slave women on the Muslim rulers of the Middle East was equally significant. As Ibn Hazm noted, in the Middle East the mothers of most Abbasid caliphs were Caucasian sexual slaves, often of Greek, Balkan, or Persian origin. In Egypt, slaves of Turkish, Mongol, Caucasian (Circassians, Georgians, Greeks or Rum, Frankish), and other origins constituted a dynasty, the Mamluks, that lasted for several generations.