During the late 800s, as the Abbasid caliphate reconsolidated after the Anarchy of Samarra, Central Asia witnessed an economic boom which was probably one of the most sudden and dramatic in the course of global history. Although there were numerous social, political, and cultural factors, one of the most important material factors was the opening of silver mines in the Hindu Kush and the massive mint at Tashkent (Ar. al-Shash, modern Tashkent in Uzbekistan).

Numbers in medieval sources must always be treated with caution, but even taken with a grain of salt, the silver production reported for the Abbasid caliphate is astounding. In the 980s, the geographer al-Maqdisi estimated that the mints of al-Shash processed 30 tons of silver annually. By comparison, the Potosí silver mine which bankrolled the Spanish Empire produced about 40,000 tons of silver spread out over 200 years. The great Swedish historian Sture Bolin estimated that in the year 800, the caliphate was generating an income of 400 million dirhams, or about 25 times the total world production of silver in 1500.

To give a bit of perspective for the effects of this Islamic silver boom on the Viking Age, consider the Spillings hoard. This hoard was buried on Gotland in the Baltic Sea around 871. It's the largest silver treasure of the Viking Age, consisting of 14,000 dirhams and scraps of silver jewelry and bars. Altogether, the coins and scrap comprise a grand total of 67 kg / 148 lbs of silver.

From an Islamic perspective, that's nothing: 0.25% of the annual production from al-Shash, and 0.0035% of the caliphate's annual budget. According to one source, the minimum a soldier would accept for pay was 200 dirhams: the Spillings hoard could keep 70 soldiers in the field for a year, or hire a modest-sized army of 25,000 troops for a day.

Within the longer scope of Scandinavian history, a quick walk through any Scandinavian history museum will show that gold emerged as the prestige material during the Roman period, followed briefly by glass during the 700s, and ultimately replaced by silver during the 800s. Ultimately, as Scandinavians tried to forge networks to the economic powerhouses of the Mediterranean and Central Asia, they tended to rely on whatever those complex societies offered them as means of exchange.