At one of the rock shows in Arizona this spring I
saw a beautiful cabochon labeled “Blue Quartz” with attributes of being able to
stimulate new and better relationships, and to remove personal fear of others. Although I am far from a mineralogist, something
didn’t look quite right to me--quartz it was not. The gentleman selling the cab did volunteer that that
the original pre-cab rock came from an old collection that in turn was garnered
from “a clip mine near Yuma”. He was
uncertain what a clip mine was!
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Top section of dumortierite slab. The pyrophyllite? seems stained with
iron. The upper portion is “fresh”
dumortierite from a “break”. The slab is
~ 12 cm. in length.
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I inquired about “blue quartz’ later on in the month
at a dusty little rock shop. Wow, the
proprietor took me over to a beer flat and showed me slabs of blue material and
told me it was a local mineral called dumortierite---and came from the Clip
Mine down near Yuma in southern Azizona. Serendipity!
So, I purchased a nice slab of the mineral complete with some
wonderful “blue markings”.
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Reverse of above photo; slab is sawed. Note that I am uncertain if both shades of
blue, light and dark, represent dumortierite, or if they are two different
minerals.
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Dumortierite is a a rather uncommon aluminum
borosilicate, (Al.Fe)7BO3(SiO4)3O3. Although it may form nice slender crystals,
most of the time the mineral is composed of
fibrous aggregates that generally are blue to violet in color (although
green, pink, brown and green colors sometimes appear). Dumortierite is about as hard as quartz (7
Mohs), has a vitreous luster, and occurs both in metamorphic and igneous rocks (aluminum
and boron rich). The rock shop
proprietor told me that polished specimens/slabs are commonly observed in southern
Arizona and adjacent California but seem rare elsewhere.
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Photomicrograph of slab—note reflected parallel saw mark. White mineral is quartz. Width of blue band
is ~ 1 cm.
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The specimen that I purchased is a mixture of
dumortierite, quartz, a soft clay-like mineral (probably pyrophyllite) and some
other unidentified minerals. In places the pyrophyllite? on the slab seems
covered by iron staining.
As for the Clip Mine, www.mindat.com
noted it is “a former underground Pb-Ag-V-Fe-Mn-Sr-Baryte-Fluorspar-Cu (Cl-Br)
mine…located about 28 miles north of Yuma, Arizona… Mineralization
is a linear ore body with argentiferous, oxidized lead minerals with silver
chloride and bromide, vanadinite, and some malachite in a gangue of ferruginous
and manganiferous calcite, quartz, fluorite, barite, pyrolusite, iron oxides,
celestine (?), gouge and brecciated wall rock, in a lensing vein in a fault
zone cutting Tertiary andesitic to dacitic flows, tuffs and breccias…It was
mined mainly in 1883 to 1887 and to a lesser degree in 1925 through 1929… Ag/T.
Silver produced was more than $1,000,000 (period values) and an additional
7,000 oz. Ag (1928-1929).”
I am going to leave my specimen of dumortierite
right here on my desk since it has a
strong ability to aid intellectual activity within the brain.... and will
assist [me]to develop enhanced mental abilities (Healing Crystals for You,
2013). I certainly need all the help
that I can get.