TANZANITE
Specimen tan-13

Dims: 0.4" x 0.3" x 0.2"(1.0 x 0.8 x 0.5 cm)

Wt: 3.80 ct

Tanzania

Figuring out where this specimen came from was not very difficult, as it consists of a single crystal of Tanzanite, a blue variety of the mineral Zoisite. The crystal has a rather well-defined form, but is incomplete due to the fact that it grew at an angle to another crystal from which it was separated. Its pleochroism is obvious- it appears to be a nearly colorless beige when viewed through its largest prism faces, whereas it has a lovely, violet-blue coloration when viewed through its smaller prism faces, and appears nearly brown in color when viewed down through its termination. It shows no man-induced damage, but there are a few heavy cracks running through it. Its luster is vitreous and it is transparent and clear, although internal fractures mar the clarity and prevent it from being viable gem material. I saw only 3 Tanzanite crystals in all the Tucson shows that were larger than this one, and they all exceeded $300 in price- and that was dealer's price! Its value, even in rough form, is amazing!

Dims: 0.4" x 0.3" x 0.2" (1.0 x 0.8 x 0.5 cm)

Wt: 1.3 g

Umba valley (near Tanga), Tanzania

This small thumbnail specimen is one of only a few Tanzanite crystals that we have seen available in the past year! This specimen is actually composed of two small crystals that have grown together and almost appear as one. Though their orthorombic form is not as pronounced as some that I have seen, it is still definite and visible, and there is very little human-induced damage evident. Their edges are somewhat rounded, but still visible, and their faces are uncommonly smooth, as most crystals of this material that I have seen show substantial striation. Their luster is bright and vitreous. The crystals both have the deep violet and blue colorations that are indicative of this pleochroic gemstone, and were likely heat-treated, as I see no evidence of the tan-to-brown coloration that is usually present in untreated stones. Both are transparent and quite clear, with the most noticeable flaws being several large internal fractures. One could conceivably cut a small stone or two out of this specimen, but it is probably not worth the labor. It is a really pretty little specimen, though, and took a lot of searching to find.

Dims: 0.3" x 0.3" x 0.2" (0.8 x 0.8 x 0.5 cm)

Wt: 0.54 g

Tanzania

A single, small Tanzanite crystal makes up this little thumbnail specimen. It is in very good condition, showing only the breakage where it was separated from its base. Its orthorhombic prismatic form is good, as its edges are slightly rounded but still definable, and its faces are heavily striated but clean, and possess the standard vitreous luster. Due to its rather pale blue-violet color that fades to a pale brown just at its base, it is safe to say that this crystal has not been heat-treated. It is transparent and reasonably clear, though it does contain many internal fractures near its base. There is no host rock present.

Dims: 0.4" x 0.2" x 0.2" (1.0 x 0.6 x 0.5 cm)

Wt: 0.57 g

Tanzania

This specimen consists of a single orthorhombic prismatic Tanzanite crystal that is in very good condition. A small amount of breakage extends upward from the base in one small area, but the rest of the crystal shows no damage. Its form is very good, with relatively well-defined edges and striated but clean faces that possess a vitreous luster. Like most Tanzanite that is not heat-treated, it has a pale blue-violet coloration that fades to a pale brown towards its base. The crystal is transparent and generally clear, though it does contain several internal fractures.

Dims: 0.5" x 0.3" x 0.2" (1.2 x 0.8 x 0.6 cm)

Wt: 0.95 g

Tanzania

The Tanzanite crystal that comprise this specimen has obviously been heat-treated, as its blue-violet coloration is relatively deep, and there is none of the brown coloration that one would expect in untreated material. It is in excellent condition, showing only the damage from its separation from its base. Its orthorhombic prismatic form is warped but still definite, as most of its faces are heavily and unevenly striated. Most of its edges are also somewhat rounded, though this is probably due to gradation of the striations. It has a bright, vitreous luster and is transparent and quite clear, containing only a few minor internal fractures. There is no host rock present, as usual.

Dims: 0.4 x 0.3 x 0.3" (1.0 x 0.8 x 0.8 cm)

Wt: 0.83 g

Tanzania

A single untreated Tanzanite crystal comprises this small thumbnail specimen. It is in excellent condition, showing only a small amount of fresh damage near its termination. Its orthorhombic prismatic form is very good, with generally well-defined edges and striated but clean faces that possess the standard vitreous luster. Its pleochorism is obvious, as its color is a pale blue when viewed through either of its two largest prism faces, but is much more violet in coloration when viewed through any of its smaller prism faces. It also shows a pale brown color when viewed from either its top or through its base; ergo, it has not undergone heat-treating. A few very minor internal fractures run along the lower portions of its main prism faces, but the crystal appears to be flawless, otherwise. Like all of our Tanzanite specimens, there is no host rock present. One could conceivably cut a stone from this piece, but it would not have uniform coloration without heat-treatment.

Dims: 0.4 x 0.3 x 0.3" (1.0 x 0.8 x 0.8 cm)

Wt: 0.7 g

Merelani, Tanzania

This small specimen consists of a single, very well-formed Tanzanite crystal that is in excellent condition. Its orthorhombic prismatic form is excellent, with well-defined edges and striated but clean faces that possess a vitreous luster. Its pleochroism is evident, as from some angles it appears to be pale blue, while from others it has a beige or a violet color. Though the crystal is transparent and quite clear, it contains several large internal fractures, some of which reach the surface in some spots. There is no host rock present, of course.

Dims: 0.5 x 0.5 x 0.2" (1.3 x 1.3 x 0.5 cm)

Wt: 2.0 g

Merelani, Tanzania

A slightly warped Tanzanite crystal makes up this specimen. It is in excellent condition, showing very little damage. Though it is somewhat warped- it looks as if 2 parallel crystals grew into each other- its orthorhombic prismatic form is still very good, with well-defined edges and clean faces that possess a vitreous luster. It has been heat-treated, but pleochroism is still visible, in that it has a pale violet color when viewed from some angles and a deeper, blue-violet color when viewed from others. It is transparent and moderately clear, containing a few large internal fractures, one of which reaches the surface in one or two areas. There is only a very small amount of a sulfide-laden host rock attached at its base.

Dims: 0.5 x 0.5 x 0.1" (1.3 x 1.3 x 0.3 cm)

Wt: 1.1 g

Merelani, Tanzania

This Tanzanite crystal has a rather odd form but is in excellent condition, showing only one small spot of light damage at a termination. Apparently it started out as a singular, flat bladed crystal whose growth was interrupted so as to split it lengthwise. This split caused the crystal to terminate with 2 or 3 distinct, shallow pinacoidal terminations. Other than this oddity, it has very good orthorhombic form, with well-defined edges and striated but clean faces that show the standard vitreous luster. It does not appear to have been heat-treated, and so shows a pale blue color from some angles, and a slightly deeper blue-violet tinge from others. It is transparent and partly clear, but contains several internal fractures and a few inclusions. Other interference is provided by a small amount of a host rock that fills the crevice between the terminations.

Dims: 0.6 x 0.3 x 0.3" (1.5 x 0.8 x 0.8 cm)

Wt: 1.4 g

Merelani, Tanzania

Several small Tanzanite crystals extend from the broken Tanzanite base of this thumbnail specimen. These crystals are very small, ranging from 2 mm to 0.4" (1 cm) in length, and are generally in good condition, though 2 are noticeably damaged. The largest crystals are somewhat intergrown, but all have good orthorhombic prismatic form, with well-defined edges and clean faces. The piece has been heat-treated, so their moderate blue-violet color is nearly uniform. Their luster is vitreous, and all are transparent and quite clear, containing a few internal fractures that are mainly concentrated at their bases. They rest on a base of broken, heavily-fractured Tanzanite.

Dims: 0.6 x 0.2 x 0.1" (1.5 x 0.5 x 0.3 cm)

Wt: 0.7 g

Merelani, Tanzania

This single Tanzanite crystal is in very good condition- though its termination appears to be damaged, this damage occurred prior to mining, and has undergone partial healing. It appears to be made up of 2 crystals that grew parallel to and into each other. One encountered a growth interruption and formed an incomplete termination just beneath the main termination. Its orthorhombic form is otherwise good, though, with well-defined edges and striated but clean faces. It appears to have been heat-treated, and shows a pale blue-violet color from some angles and a deeper, more violet coloration from others. The Tanzanite is transparent, but are only partly clear- most of its length is clouded by intense internal fracturing that holds a dark brown inclusion. There is no host rock present.

Dims: 0.3 x 0.2 x 0.1" (0.8 x 0.5 x 0.3 cm)

Wt: 0.3 g

Merelani, Tanzania

This small Tanzanite crystal almost cannot be called Tanzanite, due to its pale yellow-brown coloration. It is damaged in the fact that one prism face has been cleanly cleaved off, leaving a flat, but slightly uneven face and one visible conchoidal ding on an adjacent face. Its orthorhombic form is quite good where intact, with well-defined edges and clean faces that possess the standard pearly luster. At the very base of the crystal is a narrow band of violet coloration that is almost in the form of a phantom, as its shape takes on that of the termination. It is transparent and quite clear, containing a few small internal fractures near the base on one side. As usual, there is no host rock present.

Dims:0.2 x 0.1 x 0.1" (5 x 3 x 3 mm)

Wt: 0.3 g

Merelani, Tanzania

This tiny Tanzanite crystal is in good condition, showing some noticeable damage on 2 of its prism edges. It is otherwise intact, however, and has excellent orthorhombic form, with well-defined edges and clean faces. Its vitreous luster is standard for its species, and though it has been heat-treated, one can still see its pleochroic properties- it has a pale blue-violet color when viewed from some angles, and a slightly deeper, violet coloration when viewed from others. Apart from one noticeable internal fracture and a few other very tiny ones, it is transparent and very clear. There is no host rock present, of course.

Dims: 1.0 x 0.6 x 0.6" (2.6 x 1.6 x 1.5 cm)

Wt: 6 g

Merelani, Tanzania

At least 4 Tanzanite crystals rest on the sparse base rock of this thumbnail specimen. The largest of these crystals is by far the most pronounced and complete, and has dimensions of 0.5 x 0.5 x 0.4" (1.3 x 1.2 x 1.0 cm). It is in excellent condition, showing only light damage in one area that has partly healed over. Its orthorhombic prismatic form is very good, and shows heavy striations across its width. The stone has obviously been heat-treated, as its color changes only from a relatively deep blue-violet to a very deep violet and it is heavily internally-fractured, marring its transparent clarity. The sparse, dull-brown base material contains what appear to be bits of biotite and some tiny crystals that look suspiciously like hematite or bixbyite, though I doubt that they are either of these minerals.

Dims: 0.7 x 0.4 x 0.1" (1.7 x 1.1 x 0.4 cm)

Wt: 2 g

Merelani, Tanzania

This small, flat Tanzanite crystal is in very good condition, showing only the breakage at its base, and has very good orthorhombic form with an interesting, seemingly doubled termination. Its color ranges from a pale violet to a deep violet-blue, and its luster is vitreous. It is transparent and only dimly clear due to intense internal fracturing, which, with its color, suggest that the crystal has been heat-treated. There is no host material present.

Dims: 0.5 x 0.3 x 0.2" (1.4 x 0.8 x 0.5 cm)

Wt: 1 g

Merelani, Tanzania

This single Tanzanite crystal is in good condition, showing minor damage along one acute edge, and has reasonably good orthorhombic prismatic form. Its uniform violet color suggests that it has been heat-treated, and its vitreous luster is standard for the specie. Though transparent and moderately clear, it contains many internal fractures (most likely caused by the heat-treatment). There is no base rock present.

Dims: 1.14x0.75x0.35" (2.9x1.9x0.9cm)

Wt: 30.2 ct. (6.0g)

Mererani, Tanzania

This is a beautiful crystal of tanzanite, showing excellent form, striations, and terminations. The color is a perfect violet in the outer third of the specimen, and is smoky gray for most of the remainder. The back of the specimen looks whitish, but that is due to fractures at and just under the surface. There are a few tiny inclusions, and numerous internal fractures that ruin the otherwise excellent clarity of the crystal.