where stucco is used in a new way
Byron is heading back to Isfahan on the 31st of March 1934. On his way back, he stops and pays a visit to two Friday mosques: the Friday mosque of Na’in and the Friday Mosque of Ardistan. In the short paragraph he writes on the Friday Mosque of Ardistan we read:
“Thence [after Na’in] to Ardistan, where stucco is used in a new way, to form a kind of filigree over the brickwork. This mosque is Seljuk, dating from 1158, and has the same purity of form, though not in the same degree, as the small dome-chamber in the Friday Mosque at Isfahan.”

This short description is not 100% accurate. The mosque is pre-Seljuk, in fact, but during the Seljuk period it has been renovated extensively, and little remains of the original pre-Seljuk hypostyle mosque. The date that Byron mentions is the one written in the foundation inscription, that asserts that the building of the mosque took place in 553-555/1058-1060. Still, some parts of the earlier, original mosque can be seen here and there: pillars, columns, arches in the southern part, and the fragment of an inscription. The earliest stucco fragments that are still visible on the walls have been dated to the 10th century when the original mosque was erected.
As said, a fragment of an early epigraphic band is still visible, on the arcade running south from the southwest corner.

It contains the words:
بسمله تبارك الذى
These words can be found at the beginning of two suras: Q 25 and Q 67. According to Sheila Blair, it is probable that originally the epigraphic band contained Q 67:1, mainly because it has been used in a variety of monuments throughout Islamic lands. The content of the verse is:
“Blessed is He in whose hand is dominion, and He is over all things competent”.
The Friday Mosque of Ardistan has much in common with the Friday Mosque of Na’in, and even if it seems a case that Byron visited the two mosques in the same day, one next to the other, probably it is not. The style of the inscription is similar (even if stylistically, in Ardistan, it seems to have been carried out at later date), as is the original date of construction of the mosque. The two cities are set in a similar geographical area, both of them being just outside the Great Salt Desert.

Byron seems not to be fully aware of this and compares the mosque of Ardistan to the Friday Mosque of Isfahan. And when he takes pictures of the mosque, he focuses on the inscriptions, but he does not photograph this one, the earliest one.
Sources and further readings
Archnet.com lists a large number of images of the mosque and its various parts. Also, there you can find a description of the architecture and basic historical information.
Sheila Blair, The Monumental Inscriptions in Early Islamic Iran and Transoxiana, Brill, Leiden 1991, p. 72.
George Michell, Architecture of the Islamic World, Thames and Hudson, London 1978.
Bernard O’Kane, “Iran and Central Asia”, in Studies in Persian Art and Architecture, The American University in Cairo Press, Cairo 1995, pp. 119-139.
Arthur Upham Pope, “Architectural Ornament”, in Arthur Upham Pope and Phyllis Ackerman (eds.), A Survey of Persian Art from Prehistoric Times to the Present Vol. 3 Architecture, Its Ornament, City Plans, Gardens, 3rd ed., Soroush Press, Tehran 1977, pp. 1258-1364.