Glass and gemstone engraver. Born in Pollokshaws, Tassie began as a stonemason but, inspired by the paintings collected by the printers Robert (1707-76) and Andrew Foulis (1712-75), he studied at their Academy of Fine Arts in Glasgow in the early 1760s, alongside painter David Allan (1744-96).
Tassie moved to Dublin in 1763, where he worked with a Professor Henry Quin at the university there. Together they invented a white glass paste, a medium that Tassie used to make the medallions and reproduction cameos that became his hallmark. He moved to London in 1766 and set up what became a highly successful business. He produced cameos, intaglios and particularly portrait medallions, which illustrated in profile many of the important figures of the latter part of the 18th century, including notable figures of the Scottish Enlightenment such as David Hume (1711-76), Adam Smith (1723-90), Joseph Black (1728-99), William Robertson (1721-93) and John Adam (1721-92).
He also executed copies of many classical pieces, including an early reproduction of the Portland Vase, which was used by the Wedgwood factory to create their version in porcelain. Collectors from all over the world sought his work, with Catherine the Great his most important patron.
He was joined in his business by his nephew, William Tassie (1777 - 1860), who was also to inherit his collection of medallions.
Tassie died in London and lies buried at Southwark (London).