Kröhnkite
Kröhnkite is just an uncommon copper that is the hydrated mineral that is extremely soft by having a Mohs hardness of 2.5 – 3.0. The formula of Kröhnkite is Na2Cu(SO4)2 • 2H2O (Hydrated Sodium Copper Sulfate) and its molecular weight is 337.68 gm. Hydrated means it really is susceptible to dehydration and must be kept protected that it contains water in its chemical formula meaning. It is also readily dissolvable in water. When coming to the crystal habit of this stone is Crystals are pseudo-octahedral, equant to short prismatic along [001] or [100], to 7 cm; typically they exhibit {110}, {011}, {010}, {021}, {111}, with over two dozen more forms recorded. In crusts and aggregates, granular, massive. Kröhnkite is an uncommon mineral that is secondary to the oxidized zone of copper deposits, typically in very arid climates. It is found in colors of sky-blue to the greenish blue-green that is becoming and on publicity. Faceted gems are extremely rare but really attractive because of its colors that are wonderful.
Distribution: In Chile, amply and in big crystals from Chuquicamata, at Quetena, west of Calama, and at Collahuasi, Antofagasta; from El Cobre de Mejillones and in the Incahuasi district, Atacama. In Wheel Hazard, St. Just, Cornwall, England. From the Recsk copper deposit, Mátra Mountains, Hungary. At Capo Calamita, Elba, Italy. From Broken Hill, New Southern Wales, Australia.
| Category: | Sulfate mineral |
| Chemical Formula: | Na2Cu(SO4)2 • 2H2O |
| Hydrated Sodium Copper Sulfate | |
| Molecular Weight: | 337.68 gm |
| Composition: | Sodium | 13.62 % | Na | 18.35 % | Na2O |
| Copper | 18.82 % | Cu | 21.19 % | Cu2O | |
| Hydrogen | 1.19 % | H | 10.67 % | H2O | |
| Sulfur | 18.99 % | S | 47.42 % | SO3 | |
| Oxygen | 47.38 % | O | |||
| 100.00 % | 97.63 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals are pseudo-octahedral, equant to short prismatic along [001] or [100], to 7 cm; typically they exhibit {110}, {011}, {010}, {021}, {111}, with over two dozen more forms recorded. In crusts and aggregates, granular, massive. |
| Twinning: | Common on {101}, may be heart-shaped. |
| Cleavage: | Perfect on {010}; poor on {101} |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 2.5 – 3.0 |
| Density: | 2.90 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Other: | Readily soluble in water. |
| Color: | Sky-Blue to pale Blue or Greenish Blue, becoming Green and opaque on exposure; pale Blue to Colorless in transmitted light. |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous |
| Refractive Index: | 1.544 – 1.601 Biaxial ( – ) |
| Birefringence: | 0.057 |
| Dispersion: | Weak |
| Pleochroism: | None |
