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Hardness (or Mohs Hardness) : 7 to 7.5
RI (Refractive Index) : 1.620 to 1.650 birefringence from 0.014 to 0.021
SG (Specific Gravity) : 3.00 to 3.10
| Dimensions in mm | Carat |
| 2,0 | 0,04 |
| 2,5 | 0,07 |
| 3,0 | 0,12 |
| 3,5 | 0,16 |
| 4,0 | 0,29 |
| 4,5 | 0,35 |
| 5,0 | 0,52 |
| 5,5 | 0,66 |
| 6,0 | 0,86 |
| 7,0 | 1,65 |
| Dimensions in mm | Carat |
| 4x3 | 0,15 |
| 5x3 | 0,24 |
| 6x4 | 0,48 |
| 7x5 | 0,82 |
| 8x6 | 1,22 |
| 9x7 | 1,85 |
| 10x8 | 2,59 |
| 11x9 | 3,63 |
| 12x10 | 4,52 |
| 14x10 | 5,43 |
| Dimensions in mm | Carat |
| 4x2 | 0,09 |
| 5x2,5 | 0,18 |
| 6x3 | 0,27 |
| 8x4 | 0,60 |
| 10x5 | 1,15 |
| 12x6 | 1,74 |
| 15x7 | 3,33 |
| 16x8 | 3,97 |
| 18x9 | 5,93 |
| 20x10 | 8,62 |
| Dimensions in mm | Carat |
| 3,0 | 0,09 |
| 4,0 | 0,21 |
| 4,5 | 0,38 |
| 5,0 | 0,46 |
| 5,5 | 0,65 |
| 6,0 | 0,77 |
| 7,0 | 1,24 |
| 8,0 | 1,75 |
| 9,0 | 2,41 |
| 10,0 | 3,59 |
| Dimensions in mm | Carat |
| 4x3 | 0,21 |
| 5x3 | 0,28 |
| 6x4 | 0,35 |
| 7x5 | 1,18 |
| 8x6 | 1,73 |
| 9x7 | 2,51 |
| 10x8 | 3,84 |
| 11x9 | 5,24 |
| 12x10 | 6,48 |
| 14x10 | 6,66 |
| Dimensions in mm | Carat |
| 5x3 | 0,20 |
| 6x4 | 0,40 |
| 7x5 | 0,69 |
| 8x5 | 0,88 |
| 9x6 | 1,41 |
| 10x7 | 1,92 |
| 12x8 | 3,08 |
| 14x9 | 4,33 |
| 15x10 | 5,65 |
| 16x12 | 8,32 |
| Dimensions in mm | Carat |
| 2,0 | 0,05 |
| 2,5 | 0,08 |
| 3,0 | 0,16 |
| 3,5 | 0,22 |
| 4,0 | 0,34 |
| 4,5 | 0,53 |
| 5,0 | 0,62 |
| 5,5 | 0,75 |
| 6,0 | 1,12 |
| 7,0 | 1,82 |
The main deposits are in Brazil, Nigeria and Mozambique.
Heat-treatment is very common for tourmalines.
They might also be filled with oil, wax or resin if they have cracks, or with epoxy resin if they have large fractures.
Tourmaline attracts dust and therefore needs a regular cleaning.
- Avoid ultrasound and steam jets
- Avoid heat and thermal shocks as it may change the gem’s colour or enlarge a pre-existing fracture
- Keep treated tourmalines away from acidic substances as well.