The Mineral
AUTUNITE
(under longwave UV light)
The structure is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphates and uranium groups lie in sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness.
Autunite can lose water and convert to a different mineral called meta-autunite-I of the meta-autunite/meta-torbernite group of minerals and with heating can produce a meta-autunite-II mineral. Oddly, neither mineral is found in nature in any appreciable abundance. However, the conversion is irreversible and ongoing, and all collection specimens of a certain age are at least partially converted. Eventually after many years the meta-autunite will powder, and the specimen will be ruined. Fine autunite specimens should be stored in a closed container to avoid water loss. Some drastic measures have been attempted on fine museum quality specimens to thwart the conversion to meta-autunite, including lacquering. Remember, this is also a radioactive mineral and should be stored away from other minerals that are affected by radioactivity, and human exposure should be limited.
PHYSICAL CHARACTERISTICS:
- Colors are various shades of dark green to bright "lemon" yellow, often with a mixture of yellow and green shades in one specimen.
- Luster is vitreous to pearly on the main pinacoid.
- Transparency crystals are translucent to opaque.
- Crystal System is tetragonal; 4/m 2/m 2/m
- Crystal Habits include tabular square crystals dominated by two pinacoid faces. Crystals are often in parallel growths that can have a "fanned-out" look or in rosetta clusters. Also as crusts, earthy masses, foliated and scaly aggregates.
- Cleavage is perfect in one direction.
- Fracture is uneven.
- Hardness is 2 - 2.5
- Specific Gravity is approximately 3.1 - 3.2 (slightly above average for translucent minerals)
- Streak is yellow.
- Associated Minerals are torbernite, meta-torbernite, uranocircite, uranophane, uraninite and other uranium minerals.
- Other Characteristics: fluorescent yellow-green, radioactive, somewhat pleochroic and thin crystals or cleavage sheets are bendable.
- Notable Occurences include Autun, France; Cornwall, England; Mitchell Co., North Carolina and Mt. Spokane, Washington, USA; Zaire; Bergen, Germany and Portugal.
- Best Field Indicators are color, crystal habit, fluorescence, radioactivity, associations and flexible crystals.
 Amethyst Galleries' Mineral Gallery MINERALS |
AUTUNITE specimen aut-1
$ 36.00
$ 36.00
Dims: 7/8" x 1/2" x 7/16"
Wt: 2.4 g
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
Made up entirely of Autunite, this specimen consists primarily of a stack of tabular platelets that have separated from each other at each end of their lengths, making what I call a "bow tie" form. The bright yellow color is fabulous! This specimen is quite delicate, though, and should be handled as little as possible and with great care when necessary.
aut-1 ($ 36.00)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-2
$ 25.00
$ 25.00
Dims:1/2" x 1/2" x 3/8"
Wt: approx. 1 g
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
This delightfully bright yellow book of tablular autunite crystals has no matrix to speak of. It is extremely delicate, with small platelets ready to flake off of it, so even opening the container that it's in is not advisable. It registers quite busily on a geiger counter, and has a lovely bright green fluorescence under shortwave UV radiation.
aut-2 ($ 25.00)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-3
$ 25.00
$ 25.00
Dims:3/4" x 1/4" x 3/8"
Wt: approx. 1.4 g
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
Several small stacks of platy, crystal sheets of autunite make up this thumbnail specimen. There is a small amoumt of a host rock that has broken free and is roaming around inside the container, which should be kept closed due to its high breakability. The color, a classic hallmark of uranium minerals, is a standard bright lemon-yellow color that glows a similarly bright green under a UV light. This specimen is quite pretty, and on the money for the acquirer of radioactive goodies.
aut-3 ($ 25.00)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-4
$ 45.00
$ 45.00
Dims: 1.0" x 0.9" x 0.6" (2.5 x 2.3 x 1.5)
Wt: 7.6 g
Trancoso, Portugal
This is one of only a few specimens that I have seen come from Portugal. This particular piece consists of a cluster of intergrown "books" of micaceous Autunite platelets. They are generally in moderately good condition, as there are a few substantial areas of damage. The platelets are small, not exceeding 0.2" (5 mm) in diameter, and have rather warped forms due to their intense intergrowth. They have a greenish-yellow coloration and a pearly luster, and are nearly opaqe, showing only a dim translucence at some points. There is a small amount of a dull, rust-colored host rock scattered about on the piece, but no other host material.
aut-4 ($ 45.00)
Trancoso, Portugal
AUTUNITE specimen aut-5
$ 25.00
$ 25.00
Dims: 0.7 x 0.4 x 0.4" (1.8 x 1.0 x 1.0 cm)
Wt: 0.9 g
Malacacheta, Minas Gerais, Brazil
This small thumbnail specimen consists of a few intersecting "books" of Autunite platelets. These books do not exceed 0.4 x 0.4 x 0.1 (1.0 x 1.0 x 0.3 cm) and are in moderately good condition, as a few of them are considerably damaged. Those that are intact show good tetragonal tabular form, with sharp edges and clean faces that possess a pearly luster. Their color is the obligatory bright, greenish-yellow that is common for this mineral, and only the thinner books show any appreciable translucence. There is no host rock present on this specimen. I have affixed it to the inside of a domed plastic thimble box for display and protection with a small piece of an adhesive putty.
aut-5 ($ 25.00)
Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-6
$ 35.00
$ 35.00
Dims: 0.7 x 0.5 x 0.3" (1.8 x 1.3 x 0.8 cm)
Wt: 1.8 g
Malacacheta, Minas Gerais, Brazil
Another Brazilian specimen, this small piece consists of 3 or 4 partly-intergrown "books" of tetragonal tabular Autunite crystals. The specimen is generally in excellent condition, as only a few of these books show any obvious damage. All have excellent form, with sharp edges and clean faces that possess a pearly luster. They have the standard bright greenish-yellow coloration of Autunite and are generally opaque, though the smaller, thinner books do show noticeable translucence. The specimen has only a very small amount of a rust-colored host rock attached to it. I have affixed it inside a domed thimble box with an adhesive putty for display and protective purposes.
aut-6 ($ 35.00)
Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-7$ 120.00
Dims: 1.3 x 1.3 x 0.5" (3.3 x 3.3 x 1.3 cm)
Wt: 9.2 g
Malacacheta, Minas Gerais, Brazil
This lovely specimen consists of at least 5 "books" of tabular Autunite crystals that are held together through intergrowth with themselves and a few small tabular albite crystals. The Autunite books are generally in excellent condition, showing only a small amount of human-induced damage. Their tetragonal tabular form is excellent, with sharp edges and smooth faces that possess a pearly luster. Needless to say, they have the bright yellow coloration that is a primary characteristic of this mineral and are only dimly translucent even under halogen light. There is a substantial amount of a rust-colored, powdery material scattered about on the piece, but most of this appears to be a decomposition residue from what may have been the base rock. The albites are of the tabular variety known as cleavelandite and are in good condition. They show the standard pseudohexagonal tabular form and are colorless, transparent, and mostly clear.
aut-7 ($120.00)Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-8
$ 35.00
$ 35.00
Dims: 1.0 x 0.6 x 0.4" (2.5 x 1.5 x 1.0 cm)
Wt: 13.3 g w/ specimen box
Daybreak Mine, Spokane, Washington, U.S.A.
A radiating "sheaf" of almost parallel, stacked Autunite tablets makes up this thumbnail specimen. All are in very good condition, as there is little visible damage, and show somewhat warped but still definable tetragonal form, with sharp edges and clean faces where visible that possess the standard pearly luster. All have the standard bright yellow coloration, but this is dulled slightly by the presence of rust staining and a rather odd, dark green coloration. As with most of such specimens, the blades are opaque. There is no host rock present on the piece, and it has been glued into a small cubic plastic specimen box for display and protection.
aut-8 ($ 35.00)
Daybreak Mine, Spokane, Washington, U.S.A.
AUTUNITE specimen aut-9
$ 50.00
$ 50.00
Dims: 1.1 x 1.0 x 0.7" (2.8x 2.5 x 1.8 cm)
Wt: 15.8 g w/ specimen box
Daybreak Mine, Spokane, Washington, U.S.A.
This thumbnail specimen consists of at least 10 partly intergrown "sheaves" of almost parallel, radiating Autunite blades. These blades range in length from less than 0.2" (5 mm) to 0.7" (1.8 cm) and are generally in very good condition, though there is some obvious damage in a few areas. All have excellent tetragonal form, with well-defined edges and clean faces that possess a pearly luster. They have the standard yellow color that is dulled by the presence of rust staining and a greenish-black discoloration that is concentrated mostly at the base of each sheaf. There is no host rock present, and the specimen is hot-glued inside a small specimen box for display and protective purposes.
aut-9 ($ 50.00)
Daybreak Mine, Spokane, Washington, U.S.A.
AUTUNITE specimen aut-10
$ 40.00
$ 40.00
Dims: 0.9 x 0.9 x 0.7" (2.3 x 2.3 x 1.8 cm)
Wt: 18.1 g w/ specimen box
Daybreak Mine, Spokane, Washington, U.S.A.
A spray of somewhat compact, radiating Autunite blades comprises this thumbnail specmien. It is in very good condition, showing only a few minor scuff marks on its surfaces. The tetragonal blades that make up the spray are packed rather tightly together, but their form is reasonably good, with somewhat rounded but definable edges and relatively clean faces that possess a pearly luster. They are generally a yellow color, but substantial portions of the spray have a dark, green-black coloration that is likely due to pseudomorphing or decomposition. There is no host rock, and the specimen is hot-glued into a square plastic specimen box.
aut-10 ($ 40.00)
Daybreak Mine, Spokane, Washington, U.S.A.
AUTUNITE specimen aut-11$ 180.00
Dims: 1.3 x 1.2 x 1.1" (3.2 x 3.0 x 2.8 cm)
Wt: 0.8 oz. (21 g)
Malacacheta, Minas Gerais, Brazil
Several "stacks" of parallel Autunite growths are clustered together to form this hand specimen. The crystals that make up these stacks are in excellent condition, showing almost no damage, and have very good tetragonal tabular form, though most are tightly arranged in parallel groups. All have the standard bright yellow color with a hint of green and a bright pearly luster. Individual tablets are translucent. Only a very small amount of rusty brown and dull white host materials are present.
aut-11 ($180.00)Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-12
$ 25.00
$ 25.00
Dims:0.9x0.6x0.6" (2.3x1.5x1.5 cm)
Wt: 0.2oz. (5g)
Daybreak Mine, Mt. Spokane District, Spokane cty., Washington
This specimen consists of a small amount of matrix material covered with greenish-yellow crystals of autunite. These crystals grow to a little over 0.1" (0.3cm) in size. This specimen fluoresces brilliant yellow in short wave ultraviolet light. A few of the crystals on this specimen have been crushed, but the majority are intact.
aut-12 ($ 25.00)
Daybreak Mine, Mt. Spokane District, Spokane cty., Washington
AUTUNITE specimen aut-13
$ 36.00
$ 36.00
Dims:2.3x1.1x0.6" (5.8x2.8x1.5 cm)
Wt: 0.7oz. (21g)
Daybreak Mine, Mt. Spokane District, Spokane cty., Washington
This specimen consists of a heavy crust of autunite crystals on a small amount of matrix. The crystal crust is dark greenish-yellow at the base, gradually becoming bright yellow at the surface. With the aid of a loupe, the tetragonal crystal form can be clearly studied. This specimen exhibits very strong greenish-yellow fluorescence. There is only minor damage to this specimen.
aut-13 ($ 36.00)
Daybreak Mine, Mt. Spokane District, Spokane cty., Washington
AUTUNITE specimen aut-14
$ 48.00
$ 48.00
Dims: 0.7x0.2x0.5" (1.8x0.5x1.3cm)
Wt: 7.5 ct (1.5g)
Daybreak Mine, Mt. Spokane, Pend Orielle County, Washington, USA
This autunite thumbnail consists of a book of yellow crystals with areas colored greenish-gray. The crystals are not complete, but still show the characteristic form, color, and luster of autunite.
aut-14 ($ 48.00)
Daybreak Mine, Mt. Spokane, Pend Orielle County, Washington, USA
AUTUNITE specimen aut-15
$ 42.00
$ 42.00
Dims: 0.80x0.74x0.39" (2.02x1.88x1.00cm)
Wt: 10.90 ct (2.18g)
Daybreak Mine, Mt. Spokane, Pend Orielle County, Washington, USA
This cluster of autunite crystals is a nearly random intergrowth of flat yellow crystals. Several sections are organized as books of thin crystals, and all have a subtle curvature. Their color is varied, predominately a greenish-yellow around the edges, and more of a yellowish-green towards the centers of the clusters. They have a somewhat pearly luster and are opaque. Close examination shows that the stepped appearance of the crystals is actually just layers of crystal growth, and also that most of the crystals show some damage.
aut-15 ($ 42.00)
Daybreak Mine, Mt. Spokane, Pend Orielle County, Washington, USA
AUTUNITE specimen aut-16
$ 35.00
$ 35.00
Dims: 0.57x0.37x0.34" (1.45x0.95x0.86cm)
Wt: 0.07oz (2.1g)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
This autunite specimen consists of several intergrown books of thin rectangular crystals. Most of the autunite is a bright yellow color with a tint of green, but other parts (primarily towards the centers of the crystals) are distinctly green (with a tint of yellow). The crystals are translucent, and have a dull to pearly luster. Note that this specimen glows a bright green under both LW and SW UV light.
aut-16 ($ 35.00)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-17
$ 25.00
$ 25.00
Dims: 0.51x0.35x0.22" (1.30x0.89x0.56cm)
Wt: 4.0ct (0.8g)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
This specimen is nearly pure autunite - only a very small crust of the original host rock remains along the bottom. The autunite is yellow and translusent, with a luster I would describe as almost pearly. It is organized as a single book of thin plates with a slightly concave center, and one side is a bit larger.
aut-17 ($ 25.00)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
AUTUNITE specimen aut-18
$ 25.00
$ 25.00
Dims: 0.56x0.48x0.24" (1.43x1.21x0.62cm)
Wt: 0.02 oz (0.7g)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil
This small specimen of autunite is actually quite nice - it shows the typical habit and characteristic shapes and colorings of autunite. The color, for the most part, it an intense lemon yellow, with one side showing hints of green, and a notch that is distinctly green. This lemon is not quite ripe! The very thin, square crystals are organized in a single thick book, and the face shows a concave form. The crystals are translucent and have a pearly luster.
aut-18 ($ 25.00)
San Pedro Mine, Malacacheta, Minas Gerais, Brazil