THE MINERAL VESUVIANITE OR IDOCRASE

  • Chemistry: Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH)4, Calcium Magnesium Iron Aluminum Silicate Hydroxide.
  • Class: Silicates
  • Subclass: Sorosilicates
  • Uses: mineral specimens and the gemstone, Idocrase
  • Specimens
Vesuvianite, also known as Idocrase, is a fascinating mineral found originally on the volcano, Mt Vesuvius, hence one of the names. The other name, idocrase, is from the greek and means mixed form, an allusion to its crystals showing a mixture of other mineral forms. The crystals belong to the tetragonal symmetry class and show a square cross-section perpendicular to the long axis. Tetragonal crystals are uncommon and vesuvianite fortunately produces some very nicely shaped crystals.

Oddly enough, some of its structure is similar to that of grossularite, a garnet, which is an isometric mineral. Its structure is also interesting in that it is composed of both SiO4 groups and Si2O7 groups. Vesuvianite could be classified as a nesosilicates because of the SiO4 groups, but the higher organization of the Si2O7 groups puts it in the sorosilicate subclass.

Vesuvianite forms as a result of contact metamorphism on impure limestones and is usually found with other exotic minerals. A massive green gem variety is called californite from where it is found. It is a somewhat rare and beautiful mineral that can rival many other minerals for interest among mineral collectors.

PHYSICAL CHARACTERISTICS:

  • Color is normally green, but also can be brown, yellow, blue and/or purple.
  • Luster is vitreous or greasy to resinous.
  • Transparency crystals are transparent to translucent.
  • Crystal System tetragonal; 4/m 2/m 2/m
  • Crystal Habits include prismatic crystals with an overall square cross-section. There is usually two sets of four sided prisms with one set being dominant. The termination is usually a four sided pyramid that can be either steeply or gently sloped. The faces of the pyramids align with the faces of the prisms making an edge that is perpendicular to the length of the crystal (as opposed to the tetragonal mineral apophyllite). A pinacoid can truncate the pyramid or form the entire termination. Massive forms are common and difficult to distinguish from massive garnet.
  • Cleavage poor, in one direction lengthwise.
  • Fracture is conchoidal to uneven.
  • Hardness is 6.5
  • Specific Gravity is 3.3 - 3.5
  • Streak is white.
  • Other Characteristics: striated lengthwise and is slightly pleochroic.
  • Associated Minerals are garnets, calcite, wollastonite, diopside and serpentine.
  • Notable Occurances Asbestos, Quebec, Canada; California and the New England region of USA; Mt Vesuvius, Italy; Ural Mountains, Russia and Switzerland.
  • Best Field Indicators crystal habit, color, cleavage and localities.
VESUVIANITE specimens:
(hover for more info)
VESUVIANITE specimen ves-1
$ 25.00
Dims: 7/8" x 7/8" x 7/8"
Wt: 16 g. w/ base
Jeffrey Mine, Asbestos, Quebec, Canada
This little beauty from the productive Jeffrey Mine (I'll have to check that place out- maybe they'll give me some free stuff...) is a prime example of Vesuvianite, or as I like to say it, "Idocrase." It seems to be like a Watermelon Tourmaline in color, with a green skin surrounding a violet-pink core. There is one large crystal, double-terminated and measuring 7/8 inch long. Its interior is heavily fractured as is with many bi-colored crystals, but its sides are clean and its terminations, though oddly-formed, are complete, also with clean faces. This is one of the largest Idocrase crystals that I've seen.
no photo
ves-1 ($ 25.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-2
$ 45.00
Dims: 1-1/2" x 5/8" x 1/2"
Wt: 13 g. w/ base
Jeffrey Mine, Asbestos, Quebec, Canada
This lovely yellow-green cluster is composed of three crystals of Idocrase, ranging in length from 3/16 inch to 1-1/2 inches in length. They all show excellent crystal form, with the two smaller crystals exhibiting complete terminations. The largest crystal, though having a broken tip, shows that a definite layering pattern occurred in the growth. This is a very beautiful specimen of an uncommon mineral, and makes a great addition to a collector's curio-cabinet.
no photo
ves-2 ($ 45.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-4
$ 35.00
Dims: 1-1/4" x 5/16" x 5/16"
Wt: 10.9 g. w/ base
Jeffrey Mine, Asbestos, Quebec, Canada
Though not as impressive in size as other Vesuvianite crystals that I've seen, this specimen is distinctive through its coloration. The cluster contains 4 or 5 crystals that max out at 1/2" in length and 3/16" in diameter. Each one starts out as a reddish violet at its base, and abruptly changes to a pale greenish-yellow right at the start of the termination! The crystals are translucent due to heavy internal fracturing, and have clean sides and terminations. I really like the color change on this specimen.
no photo
ves-4 ($ 35.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-5
$ 35.00
Dims: 3/4" x 3/4" x 1/2"
Wt: 8.3 g. w/ base
Jeffrey Mine, Asbestos, Quebec, Canada
This specimen has only 2 complete crystals on it, but they are impressive, nonetheless. The larger of the two measures 5/8" long by 1/4 " in diameter, while the smaller measures 3/8" x 3/16". Both rest on a matrix that is made up of red-violet fragments of shattered crystals, and both of the complete crystals have the red-violet color from their bases to the beginnings of their terminations, whereupon the color changes abruptly to a greenish-yellow. Quite pretty!
no photo
ves-5 ($ 35.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-6
$ 30.00
Dims: 0.9" x 0.7" x 0.6"
Wt: 4.4 g
Jeffrey Mine, Asbestos, Quebec, Canada
This cluster is dominated by a crystal measuring 0.5"(1.3 cm) long and 0.3"(8 mm) in diameter, with perfect complex tetragonal prismatic form. The other crystals in the cluster are smaller in both dimensions but also exhibit excellent form. The only damage that I see affects two crystals, and both are partially healed. Their luster is vitreous, and enough transparence is evident to see intense internal fracturing that destroys the crystals' clarity. Their colors are very attractive; each crystal has a pink-violet color along its prism faces, and each termination is a greenish-yellow color. The cluster is affixed to a square acrylic base with a removable putty.
no photo
ves-6 ($ 30.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-7
$ 75.00
Dims: 1.0" x 1.0" x 0.5"(2.5 x 2.5 x 1.3 cm)
Wt: 15.0 g w/ base
Jeffrey Mine, Asbestos, Quebec, Canada
This lovely thumbnail specimen consists of a cluster of Vesuvianite, or(as I prefer calling it) Idocrase crysals that occur in a tetragonal prismatic form with a square cross-section whose corners are truncated by small secondary prism faces. They have rather warped terminations, denoting irregular growing conditions towards the end of their formation. They have a vitreous luster and are translucent due to the fracturing, with small spots of transparence. Like others from this locality, their prism lengths are colored red-violet and their terminations are colored greenish-yellow. They attain a maximum length of 0.8"(2.0 cm), and all that are longer than 0.5"(1.3 cm) seem to have malformed terminations. Most of the crystals are less than 0.2"(5 mm) in length. The specimen is hot-glued onto an acrylic base.
no photo
ves-7 ($ 75.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-8
$ 65.00
Dims: 2.4 x 2.2 x 1.1" (6.1 x 5.6 x 2.8 cm)
Wt: 4.5 oz. (126.6 g)
Braome, Italy
This Italian specimen consists of at least 10 tetragonal, almost tabular Vesuvianite crystals that are partly emebedded in a calcareous host rock. These crystals achieve dimensions of 0.6 x 0.6 x 0.4" (1.5 x 1.5 x 1.0 cm) and are generally in good condition, though a few are obviously damaged. All show slightly warped but good form, with well-defined edges and clean faces that possess a pearly-to-vitreous luster. Their color is a moderately deep brown and they are essentially opaque, though one of the smaller crystals has a small area of noticeable transparence. Their calcitic host rock appears to have some crystalline tendencies and is quite dirty, possessing a pale brown coloration on its surface and a milky white colored interior.
no photo
ves-8 ($ 65.00)
Braome, Italy
VESUVIANITE specimen ves-9
$ 125.00
Dims: 1.5 x 1.2 x 0.9" (3.8 x 3.0 x 2.3 cm)
Wt: 1.15 oz. (32.8 g)
Jeffrey Mine, Asbestos, Quebec, Canada
Part of a large cluster of heavily intergrown Vesuvianite crystals makes up this specimen. Many of the crystals are broken, but close examination will reveal that most of these were broken prior to mining, and have undergone faint, subtle partial-healing. These crystals range in length from 0.2" (5 mm) to 0.8" (2.0 cm) and even with their intense intergrowth are still in excellent condition, showing well-defined edges and clean faces that possess a vitreous luster. All are colored violet with a hint of red along their prism lengths, but fade to a pale yellow green near their terminations. All are transparent but only dimly clear at best due to intense internal fracturing and multiple inclusions. Their paler terminations tend to be slightly clearer, but are still internally-fractrured. There is no host rock present on the piece, which has been hot-glued onto an acrylic base.
no photo
ves-9 ($125.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-10
$ 310.00
Dims: 2.2 x 1.6 x 1.5" (5.6 x 4.1 x 3.8 cm)
Wt: 4.07 oz. (115.4 g) w/ base
Jeffrey Mine, Asbestos, Quebec, Canada
This hand specimen consists entirely of intergrown Vesuvianite, or Idocrase crystals. These crystals reach lengths of at least 0.8" (2.0 cm) and diameters of 0.3" (8 mm). Though there is much damage visible on the piece, most of the crystals are intact and in good condition. Their tetragonal prismatic form is very good, and most crystals have double complex pyramidal terminations. Their edges are generally well-defined and their faces are basically clean, possessing a vitreous luster. Their color is intriguing, as one "side" of the piece is made up of crystals that are entirely yellow-green in color, whereas the rest of the crystals have reddish-violet prism lengths and pale yellow-green terminations. All are at least translucent, and some are quite transparent, though they are internally-fractured as a rule. There is no host rock or any other material visible on the piece.
no photo
ves-10 ($310.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-11
$ 99.00
Dims:1.4x1.0x0.8" (3.6x2.5x2.0 cm)
Wt: 1.0oz. (28g)w/base
Jeffrey Mine, Asbestos, Quebec, Canada
This thumbnail specimen consists of an extremely intergrown cluster of vesuvianite crystals. There is no matrix material present. The largest vesuvianite crystal reaches 0.7" (1.8cm) in length. At least two of the crystals are double terminated, although some of the termination faces are obscured by other crystals. This specimen shows only minor damage, as a result of being pried from the host rock. This specimen is firmly glued to a clear acrylic base.
no photo
ves-11 ($ 99.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-12
$ 25.00
Dims: 1.2x0.5x1.5" (3.0x1.9x3.8 cm)
Wt: 0.42 oz. (11.9g)
Jeffrey Mine, Asbestos, Quebec, Canada
This thumbnail of vesuvianite has a very pale brown color, nearly colorless. The specimen is composed of hundreds of tiny and well-formed crystals which are individually specular and reflect light very well. The crystals are striated, which is very apparent in the light reflected from their crystal faces. Examination with a loupe reveals that the crystals are two colors - some are pale green, and some are pale purple - it is merely the overall appearance that looks pale brown.
no photo
ves-12 ($ 25.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-13
$ 53.00
Dims: 1.9x1.0x0.8" (4.9x2.6x2.2 cm)
Wt: 1.05 oz. (29.8g)
Jeffrey Mine, Asbestos, Quebec, Canada
This assemblage of vesuvianite crystals has an excellent green color. The crystals are translucent to transparent, although the many internal fractures create much of the translucent appearance - the crystals are quite transparent where thin. At least one crystal, perched across the others, has excellent form and termination, although all of the crystal exhibit some damage.
no photo
ves-13 ($ 53.00)
Jeffrey Mine, Asbestos, Quebec, Canada
VESUVIANITE specimen ves-14
$ 75.00
Dims: 0.8x0.8x1.0" (2.0x2.1x2.5 cm)
Wt: 0.5 oz. (13.2g)
Jeffrey Mine, Asbestos, Quebec, Canada
This pleasing lavender vesuvianite specimen is comprised mostly of a single large crystal, growing on an intergrown crystalline mass, and with a few small crystals upon it. While the crystals are transparent, their many internal fractures give an overall translucent appearance. At first, I thought that both ends of the large crystal were broken, and I used a loupe to try to detect if it was fracture or cleavage, only to find that all of the "broken" surfaces are covered with hundreds of tiny vesuvianite crystals! The crystal appears to have fractured into its present size and healed - I did not detect any human induced damage.
no photo
ves-14 ($ 75.00)
Jeffrey Mine, Asbestos, Quebec, Canada
 

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