Skip to content

Cart

Your cart is empty

Article: Is D Block Tanzanite Better ?

Is D Block Tanzanite Better ?

Is D Block Tanzanite Better ?

What Is “D Block” Tanzanite — And Is It Really Better?

I’ve spent years working on the TanzaniteOne mine site, visiting the slopes, tunnels, and workshops, so I’ve seen firsthand what makes this gemstone special—and what’s simply myth.

The world’s only tanzanite deposit barely covers eight square miles, divided by the Tanzanian government into four “blocks.” The D Block has developed a kind of legendary reputation, often touted as producing the “finest” tanzanite.

Here’s the truth: quality doesn’t depend on which block a stone comes from.

Geologically, the single and entire tanzanite deposit slopes downward at about 42 degrees from ground level. The D Block sits over the part of the deposit closest to the surface, and we think the myth of the D Block may have started in the 1970's, when the first stones were discovered.

We surmise that stones near the top of the deposit were often naturally blue, likely due to exposure to sunlight and wildfire (which removes brown veils and reveals richer blue tones). Deeper underground, in areas like the C Block, stones were more frequently uncovered with brown tones, as they were further from the surface and less likely to have experienced natural heating. (That said, many deep-mined stones still come out beautifully blue, thanks to geological and metamorphic heat underground—which can be extreme, sometimes up to 400 meters down.)

Mining methods also vary: the D Block is largely worked by small artisanal teams, giving the surface a busy, bustling appearance, while C Block is mined with modern methods through extensive underground tunnels.

From my experience, exceptional tanzanite can come from any part of the deposit. Many sellers like to use “D Block” as a marketing label, but there’s no scientific way to verify a gemstone’s block origin, and the block itself tells you nothing about true quality.

Having visited the mine repeatedly, spoken with the miners, and handled thousands of stones myself, I can confidently say that the best way to judge tanzanite is by color, clarity, and cut, not by legend or lore.

 

Read more

Is Laser Engraved Tazanite Better?

Is Laser Engraved Tazanite Better?

Laser engraving on a tanzanite may assist identification, but isn’t necessarily a sign of higher quality, as it does not affect the color, clarity, or cut of the tanzanite.

Read more