In the tables below we can see the properties of the emerald and some important data according to its deposits:
PHYSICAL, CHEMICAL AND CRYSTALLOGRAPHIC PROPERTIES
| Chemical Formula | Al2 Be3 [Si6 O18] + Cr o V |
| Mineral Type | Group IX Silicates |
| Streak | White |
| Hardness | 7.5 – 8 Mohs |
| Specific Gravity | 2.67 – 2.78 |
| Cleavage | Imperfect on the [0001] |
| Fracture | Little Conchoidal, uneven, fragile |
| Crystal System | Hexagonal |
| Habit | Hexagonal prism with pinachoidal ending |
Source: Compilation of various gemological texts.
OPTICAL PROPERTIES
| Optical Properties | Uniaxial (-) |
| Emerald optic sign | Negative |
| Transparency | From transparent to opaque |
| Color | Green, yellowish green, bluish green |
| Luster | Vitreous |
| Refractive Index | 1.568 – 1.573 // 1.578 – 1.584 |
| Birefrigerence | 0.005 / 0.006 |
| Dispersion | 0.014 (BG), 0.009-0.013 (CF) |
| Pleochroism | Green — Blue/Green — Yellow |
| Fluorenscence | LUV: strong red | SUV: weak |
Source: Compilation of various gemological texts.
PROPERTIES OF THE EMERALDS ACCORDING TO DEPOSIT
| Deposit | Refractive Index | Birefringence | Specific Gravity | Fluorescence |
| Muzo (Colombia) | 1.584 – 1.578 | 0.006 | 2.71 | Red |
| Chivor (Colombia) | 1.577 – 1.571 | 0.006 | 2.69 | Red |
| Borbur (Colombia) | 1.569 – 1.576 | 0.007 | 2.704 | Stronge red |
| Gachalá (Colombia) | 1.577 – 1.570 | 0.007 | 2.71 | Rose |
| Bahia | 1.566 – 1.571 | 0.005 | 2.67 – 2.70 | Inert |
| Urals | 1.588 – 1.581 | 0.006 | 2.72 – 2.74 | Rose |
| Habachthal | 1.591 – 1.584 | 0.007 | 2.72 -2.76 | Inert |
| Bon Jesus das Meiras | 1.574 – 1.569 | 0.005 | 2.67 | Inert – Rose |
| Sandawana | 1.593 – 1.586 | 0.007 | 2.74 – 2.77 | Inert |
| Transvaal | 1.593 – 1.586 | 0.007 | 2.72 – 2.89 | Inert |
| India | 1.593 – 1.586 | 0.007 | 2.72 – 2.75 | Inert |
| Australia | 1.572 – 1.579 | 0.007 | 2.69 | Inert |
| Norway | — | — | 2.68 -2.73 | Red |
Source: Magazine “Las gemas y otras materias preciosas”, Volume “La Esmeralda”, Instituto Gemológico Español, 1968.
