TYUYAMUNITE
Specimen tyu-4

Dims: 2-1/4" x 2" x 1-1/8"

Wt: 3.0 oz

Grants, Valencia Co., New Mexico, U.S.A.

I have never seen this stuff before. The specimen consists of Tyuyamunite (how the heck do you pronounce that?) in a microcrystalline form. Under 15X magnification, one can see tiny crystals intermixed with a bright yellow powder. I don't think that the crystals are made up of Tyuyamunite (they appear to be colorless), but of course I may be wrong. Anyway, the powder is very heavily concentrated on at least 50% of the host rock's surface area. This stuff glows quite well under a longwave UV light source, too... I wonder if it could have some, say, uranium in it or something? Hmmm....

Dims: 2.0" x 1.1" x 0.5" (5.1 x 2.8 x 1.3 cm)

Wt: 18.8 g

Monument #2 Mine, Apache County, Arizona, U.S.A.

A very simple little piece, this specimen consists of what looks like a chunk of grainy, pale brown sandstone that has several small yellow and black patches on it. The yellow patches are, of course, the Tyuyamunite, and the black patches are most likely made up os some other uranium mineral, possibly uraninite. Only a few tiny spots respond to UV radiation, and don't show up in a captured image. It does register quite readily on a geiger counter, though. This specimen is probably just right for someone that wants only a small specimen of a uranium mineral.

Dims: 2.9" x 2.4" x 1.2" (7.4 x 6.1 x 3.0 cm)

Wt: 3.23 oz. (91.6 g)

Poison Canyon, near Grants, New Mexico, U.S.A.

One of the more unusual specimens that I have seen lately, this specimen consists of a flint or chert host rock that has a flat face, on which rest at least 5 clusters of very small Tyuyamunite crystals. These crystals show substantial damage and are very small, so magnification is suggested for their study. The crystals occur in round, flat, radiating clusters that do not exceed 0.2" (5 mm) in diameter. Needless to say, the longest crystals do not exceed half of that in length. They are very odd, as their habit appears to be bladed, wherein I expected more fibrous crystals. They almost appear to be "leafy", but their form is rather difficult to determine due to their size and the damage. They have a noticeable deep-yellow color and a pearly luster, but I cannot determine if they are translucent, transparent, or naturally opaque. The material does not glow noticeably under either longwave or shortwave UV radiation. There is a very thin, milky crust between the Tyuyamunite and the host rock, though, that glows a dull red- I am thinking that it is calcite, of course.

Dims: 2.3" x 1.8" x 1.1" (5.8 x 4.6 x 2.8 cm)

Wt: 3.57 oz. (101.4 g)

Poison Canyon, near Grants, New Mexico, U.S.A.

Another example of crystalline Tyuyamunite, the dull gray host rock of this specimen sports at least 5 discernable clusters of radiating blades. These clusters have a very regular round shape and do not exceed 0.3" (8 mm) in diameter. The largest is incomplete, as it is missing a portion of the bladed crystals, but I cannot tell if this is due to damage. The blades have a moderate yellow coloration and a visible pearly luster. It is impossible to determine their translucence or clarity. They rest on a flat bed of massive milky-white calcite that coats one face of a calcareous shale or limestone slab. One other surface of this slab shows a bright yellow discoloration where a thin dusting of Tyuyamunite occurred.

Dims: 3.5" x 2.6" x 1.2" (8.9 x 6.6 x 3.0 cm)

Wt: 9.75 oz. (276.5 g)

Poison Canyon, near Grants, McKinley County, New Mexico, U.S.A.

At least 10 small formations of tiny Tyuyamunite crystals rest on the pale brown limestone host rock of this specimen. All have the deep yellow color and pearly luster that is common for crystals of this mineral. They are probably translucent, but they are all flattened up against the host rock so that their clarity is difficult to define. Some are clustered randomly, but others radiate outwards from a central point, forming round, radiating formations. Due to their size and flatness, it is difficult to determine if any are really damaged; most of the formations appear to be in excellent condition. Besides the crystals, there are some areas of the host rock which are lightly dusted with a very fine yellow powder.

Dims: 2.2 x 2.1 x 1.7" (5.6 x 5.3 x 4.3 cm)

Wt: 4.22 oz. (119.7 g)

Chihuahua, Mexico

The dull brown host rock of this hand specimen contains many pits that are filled with powdery Tyuyamunite. The Tyuyamunite occurs as either a powder or as microscopic crystals- my loupe is not powerful enough for me to tell. It has the standard bright yellow coloration and is generally dull in luster. Accompanying it are a few patches of semicrystalline, colorless calcite that are also embedded in the host rock.

Dims: 2.7 x 1.7 x 1.5" (6.9 x 4.3 x 3.8 cm)

Wt: 3.59 oz. (101.9 g)

Poison Canyon, near Grants, New Mexico, U.S.A.

A thin dusting of Tyuyamunite rests in a hollow in the base rock of this piece. The Tyuyamunite may occur in a crystalline form, but if so, the crystals are far too small to be seen even with a loupe. It essentially occurs as a dust that coats a calcite druse. It has the standard bright yellow coloration and is dull in luster. The calcites are generally extremely warped so that often one cannot see any definable crystal form. The host material appears to be made out of limestone.