DEMANTOID, the green variety of andradite garnet


VARIETY INFORMATION:

  • VARIETY OF: Andradite garnet, Ca3 Fe2 Si3 O12.
  • USES: Gemstone.
  • COLOR: various shades of green.
  • INDEX OF REFRACTION: 1.89
  • HARDNESS: 6.5 - 7
  • CLEAVAGE: none
  • CRYSTAL SYSTEM: isometric
  • SPECIMENS
Demantoid is one of the gem varieties of the garnet mineral, andradite. Its green color is similar to peridot but with a yellowish shading. Demantoid is not the only green garnet. Uvarovite and the green grossular garnet variety called tsavorite are also cut for gems. Chromium is the coloring agent of demantoid.
DEMANTOID specimens:
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DEMANTOID specimen dem-1
$ 45.00
Dims: 2.75" x 2.25" x 0.75"(7 x 5.7 x 1.9)
Wt: 2.44 oz.(69.3 g)
Green Fire Claim, San Benito County, California, U.S.A.
At least 50 green Demantoid garnets are scattered about the surface of a flat host rock on this specimen. Their color is an olive green, but not quite as yellow as that of peridot. These crystals range in size from less than 1 mm to about 0.3"(8mm) in diameter and have a pearly luster. They are cloudy and translucent. Two of the larger crystals show signs of intergrowth with other crystals, giving them somewhat complex shapes. The garnets lie on a dark green crust that looks a lot like chlorite, but I cannot be sure. The crust, in turn, lies on what I believe to be a greenish shale base rock that resembles olivine in appearance but is too soft. I don't see too many demantoid specimens at shows I go to- I'm glad we got this one.
no photo
dem-1 ($ 45.00)
Green Fire Claim, San Benito County, California, U.S.A.
DEMANTOID specimen dem-2
$ 52.50
no photo
dem-2 ($ 52.50)
DEMANTOID specimen dem-3
$ 52.50
Dims: 2.3" x 1.5" x 1.4"(5.8 x 3.8 x 3.6)
Wt: 2.62 oz.(74.3 g)
Green Fire Claim, San Benito County, California, U.S.A.
Though the many crystals on this specimen are not as large as others that we have had available, these earn some distinction because of their higher, vitreous luster and their clarity. The Demantiod crystals don't exceed 3 mm in diameter. They have a yellow-green coloration that is somewhat reminiscent of peridot and are clean and quite transparent. They all incorporate the dodecahedral variation of the cubic form. On the opposite side of the soft, shale host rock is a small cluster of more garnets that are somewhat brown in color.
no photo
dem-3 ($ 52.50)
Green Fire Claim, San Benito County, California, U.S.A.
DEMANTOID specimen dem-4
$ 220.00
Dims: 8.0 x 5.4 x 3.9" (20.3 x 13.7 x 9.9 cm)
Wt: 6.8 lbs. (3.1 kg)
Las Vigas, Vera Cruz, Mexico
This large cabinet specimen consists of scores of tiny Demantoid crystals. These crystals do not exceed 4 mm in diameter, but are in excellent condition, showing almost no damage. Most of them show a warped but definable trapezohedral form, but a few appear to have occurred as dodecahedrons. All have a moderately pale olive-green coloration and an unusually dull, almost matte luster; only the faces of a few of the crystals sparkle with their standard vitreous luster. All appear to be transparent and quite clear. There are other, smaller beds of crystals scattered in a few other places on the host rock. One of these shows some brown crystals that are accompanied either by another mineral that I cannot identify, or they are Demantoids that are so horribly warped that they appear to have an almost prismatic habit!
no photo
dem-4 ($220.00)
Las Vigas, Vera Cruz, Mexico
DEMANTOID specimen dem-5
$ 80.00
Dims: 3.0 x 1.8 x 1.8" (7.6 x 4.6 x 4.6 cm)
Wt: 5.18 oz. (146.9 g)
Green Fire Claim, San Benito County, California, U.S.A.
This small hand specimen consists of several dozen Demantoid garnets resting in crevices in and on a green serpentine host rock. They are in excellent condition- very few show any actual damage- and range in diameter from 1 mm up to 0.3" (8 mm). All have excellent dodecahedral form, with well-defined edges and clean faces that possess a pearly-to-vitreous luster. They have a uniform, nearly olive-green coloration and are translucent or dimly transparent. They do not really stand out due to their similarity in color to their host rock, but are much shinier, of course.
no photo
dem-5 ($ 80.00)
Green Fire Claim, San Benito County, California, U.S.A.
DEMANTOID specimen dem-6
$ 30.00
Dims: 2.2 x 1.1 x 1.0" (5.6 x 2.8 x 2.5 cm)
Wt: 1.57 oz. (44.6 g)
Green Fire Claim, San Benito County, California, U.S.A.
Nineteen Demantoid crystals rest on the dull green host rock of this thumbnail specimen. The crystals are very small, ranging from 1 mm to 0.2" (5 mm) in diameter, but are in excellent condition, showing no human-induced damage. All have the standard dodecahedral form, with well-defined edges and reasonably clean faces that possess a pearly-to-vitreous luster. Their color is a pale green that has an almost olive tinge, and all are generally cloudy and translucent. The host rock on which they rest strongly resembles serpentine in that portions of it have an almost compact, fibrous habit.
no photo
dem-6 ($ 30.00)
Green Fire Claim, San Benito County, California, U.S.A.
DEMANTOID specimen dem-7
$ 42.00
Dims: 2.9 x 2.0 x 1.0" (7.4 x 5.1 x 2.5 cm)
Wt: 5.33 oz. (151.1 g)
Green Fire Claim, San Benito County, California, U.S.A.
This small hand specimen consists of at least 35 minute Demantoid crystals that rest on the dark green/brown host rock. These crystals are very small, not exceeding 0.1" (3 mm) in diameter, but are in excellent condition, showing no visible damage. They all have excellent dodecahedral form- their edges are very well-defined and their faces are clean, possessing a pearly luster. Their color is a pale, almost grass-green with a noticeable olive tinge, and all are cloudy and translucent. The host rock on which they rest looks suspiciously like serpentine, and even shows evidence of a compact, fibrous nature in some areas.
no photo
dem-7 ($ 42.00)
Green Fire Claim, San Benito County, California, U.S.A.
DEMANTOID specimen dem-8
$ 95.00
Dims: 2.2 x 2.2 x 1.2" (5.5 x 5.5 x 3.1 cm)
Wt: 3.2 oz. (91 g)
Black Lake Mine, Thetford, Quebec, Canada
A few small clusters of intersecting Demantoid garnets rest on the serpentine base of this hand specimen. The largest of the crystals measure nearly 0.4" (1.0 cm) in diameter, and are in excellent condition. However, other crystals on the piece are badly broken and mostly incomplete. Those that are intact show excellent, if incomplete, isometric dodecahedral form. All have a yellow-green color and a vitreous luster, and are transparent and moderately clear. They rest on a bed of what appears to be drusy quartz which partly covers the base rock.
no photo
dem-8 ($ 95.00)
Black Lake Mine, Thetford, Quebec, Canada

 


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