Turquoise Imitations and Fakes: Howlite, Block Stone, Reconstituted, and Gilson Synthetic
Turquoise imitations fall into two categories: materials that are not turquoise at all — howlite, magnesite, glass, plastic, and Gilson synthetic — and forms made from real turquoise material that has been so heavily processed it no longer qualifies as natural stone, such as blocked and reconstituted stone. Understanding the distinction matters because each type requires different documentation and carries a different market value.
Mateo's Field Notes
The imitation market exists because turquoise is scarce and expensive at the top end, and the visual effect is easy to approximate. Chambless explains the underlying hardness problem: "Turquoise is relatively soft, and it is estimated that at least 80 percent of it is too soft to cut successfully for jewelry without having the stone cracking, losing luster, or changing color." (~line 10500–10515.) When most natural turquoise cannot be used without treatment, and gem-grade natural turquoise commands high prices, the market pressure toward substitution and imitation is structural.
The most common non-turquoise substitute is howlite — a white mineral that dyes easily to a convincing blue-green. Lowry documents it directly: howlite is a "white mineral, dyed blue/green; commonly sold as turquoise." Magnesite is a similar mineral used the same way. Neither has any relationship to turquoise mineralogically; dye is the only connection.
On the processed-turquoise end, blocked and reconstituted stone represent opposite ends of a spectrum. Blocked stone is produced by compressing turquoise crumbs under high pressure — some mineral fragments remain, but the natural structure is destroyed. Reconstituted stone goes further: the turquoise is powdered completely and mixed with a binder to form a solid block. Reconstituted material contains real turquoise powder, but it is not natural turquoise by any standard definition.
The most technically sophisticated imitation is the Gilson synthetic. Lowry: "In the 1970s, he [Pierre Gilson] developed a synthetic turquoise that was said to be mineralogically identical in every way to natural turquoise. This process produced an imitation to the clarity and robin's-egg blue color of Persian turquoise." (~line 9990–10040.) A black matrix version was subsequently added. Lowry's careful phrase — "said to be mineralogically identical" — signals that the claim is commercially reported, not independently verified in his account. Gemological testing distinguishes Gilson synthetic from natural turquoise in laboratory settings, but not reliably by eye.
Glass and plastic imitations are the lowest-cost and most easily identified substitutes. Both appear in Lowry's account of the imitation spectrum. In period jewelry, glass trade beads imitating turquoise are documented alongside genuine turquoise beads — a collector caution that applies to historic as well as contemporary pieces.
[HELD] — A passage in Bedinger (~line 858) references the introduction of imitation turquoise in the railroad era. The OCR text is partially garbled at the name of the individual credited with introducing it. This attribution is held pending corpus verification and is not published here.
Collector's Handbook
- Howlite identification. Dyed howlite is lighter in weight than genuine turquoise of the same size. Under magnification, the dye concentrates in surface pores and veins in a pattern distinct from natural matrix. Acetone on a cotton swab will lift dye from howlite; it will not affect natural turquoise.
- Magnesite vs. howlite. Both are white minerals dyed blue-green for the turquoise market. Magnesite tends to be slightly harder and denser than howlite. Gemological testing separates both from genuine turquoise conclusively.
- Blocked vs. reconstituted — disclosure required. Both forms contain real turquoise material and are not imitations in the strictest sense, but neither is natural turquoise. Both require seller disclosure under responsible trade standards. Ask specifically: "Is this natural, stabilized, blocked, or reconstituted?"
- Gilson synthetic trap. Because Gilson synthetic may approach turquoise mineralogically, standard hardness and specific gravity tests can be inconclusive. For high-value purchases, request a gemological laboratory report that specifically addresses natural vs. synthetic origin.
- Glass and plastic — weight and temperature. Glass is cold to the touch and heavier than plastic; both are significantly heavier than real turquoise for the same volume. Genuine turquoise warms quickly in the hand; glass stays cool longer. Neither substitutes for lab testing on a significant piece.
- Price as a signal. Deep discounts on "natural turquoise" are the primary imitation flag. Natural gem-grade turquoise at market rates is not cheap. If the price seems too good, it is.
Related Entries in the Directory
For treatment taxonomy (stabilized, Zachery, fracture-sealed — materials that are still turquoise), see Natural vs. Stabilized Turquoise. Browse verified material sourcing in the Silversmith Directory.
Primary Sources
- Lowry, Joe Dan & Joe P. Lowry. Turquoise: The World Story of a Fascinating Gemstone. Gibbs Smith, 2010, ~line 9990–10040 (Gilson synthetic); howlite and magnesite entries; blocked and reconstituted stone entries; glass and plastic imitations.
- Chambless, Philip & Mike Ryan II. Turquoise in America, Part One: The Great American Turquoise Rush 1890–1910. Callais Press, 2021, ~line 10500–10515 (hardness/softness explanation of imitation market).
- Bedinger, Margery. Indian Silver: Navajo and Pueblo Jewelers. University of New Mexico Press, 1973, ~line 858 ([HELD] — imitation introduction in railroad era, OCR garbled).