The line was in place before the opening bell at Tucson's New Mineral Show.
Buyers scrambled to fill their boxes at Shannon's.
The next morning, Day 2, I was up bright and early and headed to the opening of Tucson’s New Mineral Show that was held at the site of a former “slaughter house.” I was interested in getting to one of my favorite mineral dealers, Michael Shannon. His shop happened to be in the former corral, a holding pen prior to the poor suckers heading to the hamburger house. Unfortunately (for the mineral shows) the rain came again over night and parking was muddy and wet. Although I arrived 20 minutes before opening, the line was stretched out into the street waiting for the bell!
For the last couple of years, maybe a few more, a bright lemon-yellow botryoidal mass has graced the tables of many mineral dealers. Prices on some of these specimens range into five figures and small time collectors like me need to hunt and hunt for more reasonably priced specimens. There seems to be an abundance of golf ball-size specimens that sell for one hundred dollars to over one thousand dollars-prices vary. The mineral in question is brucite, a magnesium hydroxide [Mg(OH)2]. As best that I can determine, collectable brucite is not a common mineral and “natural” brucite has little commercial value except perhaps as a source of magnesium. However, synthetic brucite is useful as a flame retardant and insulator.
I may remember brucite from days gone past as sort of a non-descript “crud” present in some metamorphic rocks. I fact, I thought brucite was some sort of a clay mineral, perhaps due to its common association with clay minerals like montmorillite and smectite, and some of the chlorite group minerals. At any rate I did not pay much attention to brucite, that is until the mineral suddenly appeared on the scene selling for “big money.”
So, what is the deal? My best answer is that a new locality in Pakistan (Killa Saifullah District, Baluchistan) showed up producing some brightly colored “lumps” of a “pretty” mineral, bright lemon yellow to pastel yellow—and the rest was history. Brucite became collectable and the larger the specimen the better. Yellow was in!
In parts of the world where geological work my be completed without risking one’s life, geologists know that brucite may form when dunite (olivine-rich rocks derived from the Earth’s mantle) is subjected to serpentinization (hydration and metamorphism common at plate boundaries), when periclase (magnesium oxide, MgO) in marble hydrates, and when certain limestones undergo low temperature alteration. My only clue to the Pakistani brucite is that some photos in MinDat show a serpentine matrix so I would assume the brucite is associated with metamorphism.
Some brucite is an attractive display mineral, no doubt about it. I tried location information about the yellow color; however, I found mostly speculation rather than facts, I suppose the answer is out there but locating such is above my pay grade.
|Botryoidal mass of brucite with pronounced pearly luster. Width of specimen ~1.2 cm. Purchased at Shaannon's.|
Besides the yellow color of collectable brucite the mineral is found shades of drab grays or blue-grays, green, and white to clear although manganese, zinc and iron impurities may offer other colors. It is quite soft ~2.5+ (Mohs), translucent to transparent, vitreous to pearly luster, and a white streak. Some specimens show fibrous crystals or tabular pseudohexagonal crystals. Brucite can be massive, botryoidal with crystals that are indistinguishable, bladed, grainy, or other habits.
|Multicolored specimen of brucite purchased at Shannon's. Note the crude rosette of fibers. Width of specimen ~1.5 cm.|
|I stayed away from this vendor!|
|I wanted, but could not afford, these variscite phosphate nodules from the Little Green Monster Mine in Utah.|