Alembic: Chemical apparatus, discovered by Jabir ibn Hayyan[8] Arabesque: The distinctive Arabesque style was developed by the 11th century, having begun in the 8th or 9th century in works like the Mshatta Facade.[9][10] Astrolabe with angular scale and navigational astrolabe: The astrolabe, originally invented some time between 200 and 150 BC, was further developed in the medieval Islamic world, where Muslim astronomers introduced angular scales to the design,[11] adding circles indicating azimuths on the horizon.[12] Chemical elements and equivalents: The work of Jabir ibn Hayyan gave the seeds of the modern classification of elements into metals and non-metals as could be seen in his chemical nomenclature.[13] The origins of the idea of chemical equivalents might be traced back to Jabir, in whose time it was recognized that "a certain quantity of acid is necessary in order to neutralize a given amount of base."