What language was the original verses of the the Quran written in?
Muhammad b.570 to d.632 was a member of the Quraish tribe who were descendants of Ishmael. The Quraish are referred to as Arabised Arabs i.e. not true Arabs. It can be seen from the below quote from Bukhari 6:61:510 that the Quraish had their own dialect and their own written language. It consequently seems logical that the original notations of the iterations dictated by Muhammad to his scribes were written in Quraish.
It appears that during the 23 years when Muhammad dictated verses of the Quran he did so to several different scribes who appear to have retained the various writings themselves. After the battle of Yamama in 633 AD when 700 Muslims who had memorized the Qur'an were killed including Sālim, who had been entrusted by Muhammad to teach the Qur'an, Abu Bakr ordered Zaid ibn Thabit, Muhammad's primary scribe, to collect the scattered pieces of the Qur'an.
Zaid ibn Thabit, said . . . ....By Allah, if he (Abu Bakr) had ordered me to shift one of the mountains it would not have been harder for me than what he had ordered me concerning the collection of the Quran... So I started locating the Quranic material and collecting it from parchments, scapula, leafstalks of date palms and from the memories of men (Bukhari 6:60:201)
All that he collected all that he could find he handed them to Umar, who, on his deathbed gave them to Hafsa bint Umar, his daughter and one of Muhammad's widows.
Uthman ibn Affan, (644 656 AD) during his reign as the third Caliph, formed a committee of prominent Quraish to place in order the various verses and produce a standard copy of the text.
This became known as al-mushaf al-Uthmani or the Uthmanic codex. It was written in Kufic, the most commonly used script in the region at that time.
Bukhari (6:61:510) records the follwing about Uthman in 653 AD:
Hudhaifa bin Al-Yaman came to Uthman at the time when the people of Sham and the people of Iraq were Waging war to conquer Arminya and Adharbijan. Hudhaifa was afraid of their (the people of Sham and Iraq) differences in the recitation of the Qur'an, so he said to 'Uthman, "O chief of the Believers! Save this nation before they differ about the Book (Quran) as Jews and the Christians did before." So 'Uthman sent a message to Hafsa saying, "Send us the manuscripts of the Qur'an so that we may compile the Qur'anic materials in perfect copies and return the manuscripts to you." Hafsa sent it to 'Uthman. 'Uthman then ordered Zaid bin Thabit, 'Abdullah bin AzZubair, Said bin Al-As and 'AbdurRahman bin Harith bin Hisham to rewrite the manuscripts in perfect copies. 'Uthman said to the three Quraishi men, "In case you disagree with Zaid bin Thabit on any point in the Qur'an, then write it in the dialect of Quraish, the Qur'an was revealed in their tongue." They did so, and when they had written many copies, 'Uthman returned the original manuscripts to Hafsa. 'Uthman sent to every Muslim province one copy of what they had copied, and ordered that all the other Qur'anic materials, whether written in fragmentary manuscripts or whole copies, be burnt. Said bin Thabit added, "A Verse from Surat Ahzab was missed by me when we copied the Qur'an and I used to hear Allah's Apostle reciting it. So we searched for it and found it with Khuzaima bin Thabit Al-Ansari. (That Verse was): 'Among the Believers are men who have been true in their covenant with Allah.' (33.23)
As can be seen, from the above quote all the original notes were burnt by Uthman presumably to prevent future argument that his compiled version was not correct. It also logically follows that the oldes survining copies of the Quran would be writtn in the Kufic script.
Arab Script
At the time of Muhammad the principal material used for writing on was hide. Of course processing a piece of animal skin to use as paper was time consuming and costly. It consequently follows that very little writing was done and few people knew how to write. In fact, even today, literacy in the Arab world is relatively low.
The Arabs usually distinguish four types of pre-Islamic script: al-Hiri (from Hira), al-Anbari (from Anbar), al-Maqqi (from Mecca) and al-Madani (from Medina). The famous author of Fihrist, Ibn Nadim (died c. 390/999) was the first to use the word 'kufic', deriving it from the hiri script. However, Kufic script cannot have originated in Kufa, since that city was founded in 17/638, and the Kufic script is known to have existed before that date, but this great intellectual centre did enable calligraphy to be developed and perfected aesthetically from the pre-Islamic scripts.
Kufic also sometimes called Hiri script is one of the oldest calligraphic form of the various Arabic scripts and consists of a modified form of the old Nabatean script. Its name is derived from the city of Kufa (in modern-day Iraq), although it was known in Mesopotamia at least 100 years before the foundation of Kufa. At the time of the emergence of Islam, this type of script was already in use in various parts of the Arabian Peninsula.