The Egyptians were seemingly the first to produce an artificial imitation of turquoise, in the glazed earthenware product faience. Later glass and enamel were also used, and in modern times more complicated ceramics, porcelain, plastics, and an assortment of assembled, pressed, bonded, and sintered products (composed of various copper and aluminium compounds) have been developed: examples of the latter include "Viennese turquoise", made from precipitated aluminium phosphate coloured by copper oleate; and "neolith", a combination of bayerite and copper phosphate. Most of these products differ markedly from natural turquoise in both physical and chemical properties, but in 1972 Pierre Gilson introduced one rather close to a true synthetic (it does differ in chemical composition owing to a binder used, meaning it is best described as a simulant rather than a synthetic). Gilson turquoise is made in both a uniform colour and with black "spiderweb matrix" veining not unlike the natural Nevada material.

Some natural blue to blue-green materials, such as this botryoidal chrysocolla with quartz drusy, are occasionally perplexed with, or used to imitate turquoise.
The most common imitation of turquoise encountered today is dyed howlite and magnesite, both white in their natural states, and the former also having natural black veining similar to that of turquoise. Dyed chalcedony, jasper, and marble is less common, and much less believable. Other natural materials infrequently confused with or used in lieu of turquoise include: variscite; faustite; chrysocolla (especially when impregnating quartz); lazulite; smithsonite; hemimorphite; wardite; and a fossil bone or tooth called odontolite or "bone turquoise", coloured blue naturally by the mineral vivianite. While rarely encountered today, odontolite was once mined in large quantities—specially for its use as a substitute for turquoise—in southern France.

These fakes are detected by gemmologists using a number of tests, relying first and foremost on non-destructive, close examination of surface structure under magnification; a featureless, pale blue background peppered by flecks or spots of whitish material is the typical surface look of natural turquoise, while manufactured imitations will appear fundamentally different in both colour (usually a uniform dark blue) and texture (usually granular or sugary). Glass and plastic will have a much greater translucency, with bubbles or flow lines often visible just below the surface. Staining between grain boundaries may be visible in dyed imitations.
Some damaging tests may, however, be necessary; for example, the application of diluted hydrochloric acid will cause the carbonates odontolite and magnesite to effervesce and howlite to turn green, while a heated probe may give rise to the acrid smell so suggestive of plastic. Differences in specific gravity, refractive index, light absorption (as evident in a material's absorption spectrum), and other physical and optical properties are also considered as means of division. Imitation turquoise is so prevalent that it likely outnumbers real turquoise by a wide margin. Even material used in authentic Native American and Tibetan jewellery is often fake or, at best, heavily treated.