THE MINERAL SCHEELITE
- Chemistry: CaWO4, Calcium Tungstate
- Class: Sulfates
- Subclass: Tungstates
- Uses: An important source of tungsten, rarely cut as gemstones and as mineral specimens.
Specimens
Scheelite is a popular mineral for collectors. It forms perfect tetragonal dipyramidal crystals that look very much like octahedrons. These pseudo-octahedral crystals are sometimes truncated with minor pyramids, but only on the top and/or bottom points of the crystal; giving evidence of their true symmetry. Other minerals that form pseudo-octahedral crystals similar to scheelite include wardite, anatase and powellite.
Powellite, CaMoO4, is isostructural with scheelite which is why it forms similar crystals. The two minerals form a series in which the tungsten of scheelite is substituted for by the molybdenum of powellite. Powellite fluoresces a yellow color while scheelite fluoresces a bright blue under short wave ultraviolet light. Of course since molybdenum can substitute for tungsten, some scheelite specimens will show a yellow fluorescence.
The crystals of scheelite can look like fluorite octahedrons which can also fluoresce. However, fluorite has perfect octahedral cleavage and a lower luster. Massive scheelite has often been mistaken for massive quartz, but then the fluorescence of scheelite is a dead giveaway.
Many prospectors for scheelite have made good use of scheelite's typically bright blue fluorescence by searching for scheelite deposits by night with ultraviolet lamps. Many old mines have even been reopened after examination of the mine shafts with ultraviolet lamps have proven that the ore is not quite yet exhausted.
PHYSICAL CHARACTERISTICS:
- Color is white, yellow, orange or greenish gray to brown.
- Luster is adamantine to greasy.
- Transparency: Crystals are transparent to translucent.
- Crystal System is tetragonal; 4/m
- Crystal Habits include the pseudo-octahedral crystals that are actually tetragonal dipyramids. Also massive and granular.
- Cleavage is indistinct in two directions and good in another (dipyramidal).
- Fracture is conchoidal.
- Hardness is 4.5 - 5.
- Specific Gravity is approximately 5.9 - 6.1 (very heavy for translucent minerals).
- Streak is white.
- Other Characteristics: Fluoresces blue (yellow with molybdenum traces) under short wave ultraviolet light.
- Associated Minerals are quartz, garnets, vesuvianite, epidote, topaz, schorl, apatite, gold, silver, molybdenite, cassiterite, wolframite and fluorite.
- Notable Occurrences include Hollinger Mine, Ontario, Canada; Saxony, Germany; Tong Wha, Korea; Brazil; Sonora, Mexico; Cornwall, England; New South Wales and Queensland, Australia and Mill City, Nevada, Atolia, San Bernardino Co., California, Cochise Co., Arizona, Utah and Colorado, USA.
- Best Field Indicators are crystal habit, color, density, luster and especially its fluorescence.
 Amethyst Galleries' Mineral Gallery MINERALS |
SCHEELITE specimen sch-1
$ 90.00
$ 90.00
Dims: 2.0" x 1.2" x 0.9"(5.1 x 3.0 x 2.3 cm)
Wt: 1.31 oz.(37.3 g)
Yaogangxian Mine, Yizhang County, Hunan Province, China
At least 10 pale brown Scheelite crystals rest on this specimen. They range in size from less than 1 mm to 0.3"(8 mm) in length, and occur in a tetragonal bipyramidal form that strongly resembles an octohedron. The crystals have an adamantine luster, are translucent and opaque, and have excellent form and little damage, which is confined to the largest crystal and one other. The largest crystal is incomplete, in effect, showing only one tetragonal pyramid and a scar where the other was broken off. They rest on a base that is made up of crystalline quartz coated with calcite that occurs in a tabular platelet form. The scheelite glows a bright blue under UV light- it is very easy to see. I like this specimen- the color and the blue fluorescence really are attractive.
sch-1 ($ 90.00)
Yaogangxian Mine, Yizhang County, Hunan Province, China
SCHEELITE specimen sch-2
$ 110.00
$ 110.00
Dims: 1.3" x 1.2" x 1.1"(3.3 x 3.0 x 2.8 cm)
Wt: 2.24 oz.(63.7 g)
Pingwu, Sichuan Province, China
A single Scheelite crystal comprises this specimen. It is in the tetragonal bipyramidal shape that is standard for this mineral, and looks a lot like an octahedron. There is considerable damage to the crystal, and it is incomplete; two points and most of one face of it are missing from where it was separated from its host rock. The crystal's color is a dull orange and even though it is translucent, some areas are transparent enough to see internal fractures within. It has a pearly luster and many triangular growth patterns on each crystal face. I have not seen a larger scheelite crystal than this one- it is quite impressive.
sch-2 ($110.00)
Pingwu, Sichuan Province, China
SCHEELITE specimen sch-3$ 220.00
Dims: 3.5" x 1.7" x 1.3"(8.9 x 4.3 x 3.3 cm)
Wt: 4.00 oz.(113.6 g)
Pingwu, Sichuan Province, China
One of the finest specimens of Scheelite I have seen, this Chinese piece consists of a single crystal in excellent condition. It is relatively large, measuring 0.7 x 0.8 x 0.9"(1.8 x 2.0 x 2.3 cm) and is in the classic tetragonal pyramidal shape of its kind. It exhibits almost no detectable damage on its upper pyramid and its termination is not quite complete, having been damaged and partially healed during its formation. Its is a dull orange color and translucent at its base, clearing to a bright, transparent golden-orange at its termination in stages. These stages are denoted by 2 parallel internal fractures that run along the basal plane. It has a vitreous luster and a small amount of triangular growth patterning on each face near the crystal's base. The crystal takes on a pseudo-octahedral shape due to the breakage surface of its host rock, which caused part of the break to cleave the crystal's underside so as to be aligned like a crystal face. The matrix itself is made from a dense mica schist that is coated with small hexagonal books of muscovite crystals.
sch-3 ($220.00)Pingwu, Sichuan Province, China
SCHEELITE specimen sch-4
$ 75.00
$ 75.00
Dims: 1.0" x 0.9" x 0.9" (2.5 x 2.3 x 2.3 cm)
Wt: 24.2 g
Yao Gang Xiang Mine, Cheng Zhu, Hunan Province, China
This small thumbnail specimen consists of a single, incomplete Scheelite pesudo-octahedron. This crystal has good form, with well-defined edges and faces that show a bright, nearly adamantine luster. Though it is incomplete, this is not due to any human-induced damage; the crystal appears to have broken during its formation and the break was partially healed over. The crystal has a pale grayish coloration and appears to be rather milky. I think that this is due to a thin layer of trasparent material coating a translucent "core". A few of the surfaces, especially in and around the partially-healed area, show some very dark material. It is a rather interesting specimen to examine.
sch-4 ($ 75.00)
Yao Gang Xiang Mine, Cheng Zhu, Hunan Province, China
SCHEELITE specimen sch-6
$ 150.00
$ 150.00
Dims: 2.7 x 2.2 x 2.1" (6.9 x 5.6 x 5.3 cm)
Wt: 3.2 oz. (90.9 g)
Pingwu, Sichuan Province, China
Maybe I should have classified this specimen as a "beryl". It consists of a single octahedral Scheelite crystal that is intergrown with 2 of the 3 hexagonal tabular beryl crystals that are present. The Scheelite has visible dimensions of 0.6 x 0.6 x 0.5" (1.5 x 1.5 x 1.3 cm) and is in excellent condition, showing no human-induced damage. Its form is moderately good, but is mostly obscured by one of the beryls; its edges are slightly rounded but somewhat well-defined, and its faces are relatively clean, possessing an adamantine luster. The Scheelite's color is a moderately dull orange with golden highlights, and it is dimly transparent, containing many internal fractures. The accompanying beryls are rather large in comparison- the largest has dimensions of 1.5 x 1.0 x 0.6" (3.8 x 2.5 x 1.5 cm), and the others are not much smaller. All are in excellent condition, showing almost no human-induced damage, and their almost tabular form is very good, with well-defined edges and clean faces that possess the vitreous luster. All are transparent and moderately clear, as they contain many noticeable cloudy inclusions and internal fractures. They are not quite colorless- all have a faint tinge of pale blue, though I would not call them aquamarines. All of these crystals are attached to a crust made up of both crystalline and massive muscovite.
sch-6 ($150.00)
Pingwu, Sichuan Province, China
SCHEELITE specimen sch-7$ 240.00
Dims: 1.9 x 1.6 x 1.6" (4.8 x 4.1 x 4.1 cm)
Wt: 6.9 oz. (196.2 g)
Pingwu, Sichuan Province, China
A single, incomplete Scheelite octahedron comprises this small hand specimen. It is the largest individual Scheelite crystal that I have seen, and it is in good condition, showing moderate human-induced damage. Its octahedral form is also good, with well-defined edges and slightly disseminated but clean faces that possess a subadamantine luster. It has the dull, golden-orange coloration that is common for specimens from this locality, and is dimly translucent but shows patches of dim transparence in a few areas. There are a few scraps of broken muscovite books attached to the surface where it was once attached to a host rock, but there is no host rock present. Though not shown, it does glow a rather bright blue under shortwave UV light.
sch-7 ($240.00)Pingwu, Sichuan Province, China
SCHEELITE specimen sch-8
$ 37.00
$ 37.00
Dims: 0.7 x 0.6 x 0.3" (1.8 x 1.5 x 0.8 cm)
Wt: 12.3 g w/ specimen box
Yaogangxian Mine, Hunan Province, China
This small thumbnail specimen consists of 4 or 5 Scheelite octahedrons resting on a quartz base. Only two of these crystals exceed 2 mm in diameter, and both of these have diameters of approximately 0.3 x 0.2 x 0.2" (0.8 x 0.5 x 0.5 cm). Both are situated adjacent to the breakage surface of the specimen, and so show considerable damage. Their octahedral form is very good, though there is an irregularity of growth on the larger crystal that results in an almost twinned point. Both have a pale brown coloration and a bright, adamantine luster, and are translucent and very cloudy. They are accompanied on the quartz base by several small calcite blades that show good form and are generally intact. The specimen is hot-glued into a square plastic specimen box.
sch-8 ($ 37.00)
Yaogangxian Mine, Hunan Province, China
SCHEELITE specimen sch-9
$ 51.00
$ 51.00
Dims: 3.2 x 2.8 x 1.6" (8.2 x 7.2 x 4.0 cm)
Wt: 6.0 oz. (170 g)
Princess Pat Mine, San Bernardino County, California, U.S.A.
The massive calcite matrix of this hand specimen contains many tiny patches of Scheelite, which under normal light are essentially invisible. When bathed in shortwave UV light, however, their bright white glow is quite easy to see. Accompanying the Scheelite are a few thin veins and patches of "hyalite" opal that glow with a green coloration. The calcite also glows, but only very dimly, with a faint orange color. A few tiny spots of a bright yellow color are also present, but I do not know what material causes this.
sch-9 ($ 51.00)
Princess Pat Mine, San Bernardino County, California, U.S.A.
SCHEELITE specimen sch-10
$ 26.00
$ 26.00
Dims: 2.8 x 1.5 x 0.7" (7.2 x 3.9 x 1.8 cm)
Wt: 1.69 oz. (48.0 g)
Princess Pat Mine, San Bernardino County, California, U.S.A.
Though this small hand specimen appears to be thoroughly unimpressive under normal light, it holds a few secrets. When bathed in shortwave UV light, it shows many small, patches of brightly-glowing white material- this material is Scheelite, and is indistinguishable from the rest of the piece in white light. Patches of a slightly dimmer, green glow represent "hyalite" opal, which is also nearly impossible to distinguish otherwise. A noticeable amount of calcite rests on the piece, but its orange glow is nearly invisible.
sch-10 ($ 26.00)
Princess Pat Mine, San Bernardino County, California, U.S.A.