In Tucson 2022 at a vendor’s tent (long forgotten the name) I picked up an interesting specimen of hemimorphite that had came from the Ojuela Mine, Mapimi, Durango, Mexico. The small crystals, associated with goethite, were nicely displayed in a Perky Box. Now, rockhounds with any familiarity of Mexican minerals know that hemimorphite [Zn4Si2O7(OH)2-H2O] crystals from Ojuela are quite common at almost any rock and mineral show. In fact, I have several specimens in my collection so why would I need to add another?
“Normal” clear and gemmy hemimorphite from Mapimi, Mexico. Width FOV !1.0 cm.
There were several reasons for this purchase: 1) the crystals are well formed and quite attractive; 2) they are blue in color; 3) specimens of blue crystals were selling for “big bucks” in the 2020 Denver show and well out of my budget; 4) I paid a measly $3 for my specimen; and 5) the color of the beautiful hemimorphite was fake-it had been dyed blue! Now, rockhounds can find dyed “agates” at almost any trinket shop or rock/mineral store but I had never seen dyed hemimorphite. It turns out that many legitimate mineral dealers, and their customers also had never seen bright blue crystals.
Bright blue, dyed hemimorphite crystals from Mapimi, Mexico. Width FOV ~1.0 cm. (top two and ~1.5 cm. lower).
In the January 2021 issue of Rock & Gem, Bob Jones, the long-time contributor to the magazine, published an article entitled On the Rocks: Much-talked-about hemimorphite lacks authenticity. Jones fully explained the known history about these fakes and how the fraud was discovered—but not before dealers and buyers had lost money! The following is information abstracted from the article.
The latest case of such fraudulent action is a group of specimens of dyed blue hemimorphite from Mina Ojuela, Mapimi, Durango, Mexico, currently being marketed. This mining area has had an outstanding reputation for producing world-class minerals of great variety for generations. Until we know exactly what has produced these blue hemimorphites, that reputation may be impacted.
Of course, bright blue botryoidal hemimorphite examples have been found at many locations throughout the world. These are entirely natural. Then, suddenly, brilliant blue crystal specimens of hemimorphite appeared from Mapimi in summer 2020.
Dealers were happy to have something new and exciting as colorful minerals sell well, especially from a locality with a sturdy reputation. Dealers are, by and large, a suspicious lot, and many were cautious of this strange, new color, but evidence of authenticity, including videos of specimens being collected in situ underground, showed they were likely natural. Many dealers bought specimens for resale before the September mineral shows. Their faith proved to be misplaced as the blue hemimorphite was finally proven to be an unnaturally dyed mineral.
Fake specimens showed up in some quantity at the shows held in Denver in September 2020. Many dealers already had plenty of specimens at this point in the year, and it appears some had invested considerable sums in this fake mineral.
Many dealers conducted tests with positive results. For example, the mystery blue mineral was seemingly impervious to most known solvents and simple testing. One interesting note is a trace of copper had shown up in initial analytical testing. Copper is a well-known blue coloring agent in minerals, so this tended to confirm the blue mineral was probably legit.
Dr. John Rakovan (Miami University, Oxford Ohio) did some preliminary testing with inconclusive results but then did more in-depth testing using Raman Spectroscopy, and this finally revealed the truth. The blue material was a dye that is almost impossible to detect and which is extremely colorfast. This result means ordinary analysis would not dislodge it or reveal its presence. Plus, the specimens’ physical characteristics appeared perfectly natural and explainable, such as blue hemimorphite crystals with snow-white calcite crystals. How was this selective dyeing done? The testing by Dr. Rakovan finally revealed the culprit. What was used is a synthetic blue pigment, called Phthalocyanine Blue BN, an organic dye. This dye is not easy to remove because it is stable, which explains why ordinary chemical tests showed nothing unusual.
MR. ROCKHOUND DOES IT AGAIN
Jones exposes fakes
Defines
blue hemimorphite
Amazing Rockhound
By the time 2022 rolled around information about the scam had traveled around the circuit and dealers with excess stock sold specimens at great discounts (and probably lost money). My label, without a dealer’s name, is quite honest as it states “Dyed.” The specimen has a prominent place on my shelf and is a great object for Show & Tell!
Hemimorphite is a hydrated zinc silicate [Zn4Si2O7(OH)2-H2O] that occurs in several environments, colors, lusters, and for decades was confused with the zinc carbonate, smithsonite [ZnCO3]. The name comes from doubly terminated crystals where the terminations have different faces (hemimorphic development). The crystals have a white streak, a vitreous luster, ~5 hardness (Mohs), are colorless and transparent to translucent, and come from the oxidized zone of zinc-bearing mineral deposits. With a zinc component of over 50%, hemimorphite is a minor ore of zinc.
In closing, I saw this little ditty on a tee shirt the other day: Duct tape can’t cure stupidity, but it can muffle the sound.
CHECK OUT THESE WEB SITES FOR DISCUSSIONS ON BLUE HEMIMORPHITE
