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. |
No comments:
Post a Comment