Editorial Feature

Krohnkite – Occurrence, Properties and Distribution

Aug 14 2013

Krohnkite was named to honor B.Krohnke, who was the first to provide analysis on the mineral. It was first discovered Chuquicamata Mine, located in the Antofagasta in Chile. This mineral belongs to the roselite group.

Properties of Krohnkite

The key physical properties of Krohnkite are as below:

Cell Data
- Space Group = P2₁/c
- a = 5.807 (1)
- b = 12.656 (2)
- c = 5.517 (1)
- Z = 2
Crystal Data
- Monoclinic.
- Point Group – 2/m.
- Crystals – 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.
- Twinning: common on {101}, heart-shaped.
- X-ray powder pattern: Chuquicamata, Chile.
  6.33 (100), 3.278 (90), 2.757 (90), 2.925 (80), 3.715 (60), 4.145 (40), 3.099 (40).

Chemical Composition

Elements	Content 1	Content 2
SO₃	47.60	47.42
CuO	23.25	23.56
Na₂O	18.89	18.35
H₂O	10.72	10.67

Optical Properties
- Transparent
- Lustre – vitreous
- Color- sky-blue to pale blue or greenish blue, becoming green and opaque on exposure
- Optical Class – Biaxial (-).

How to Identify Krohnkite

The color of krohnkite varies from sky-blue to pale blue or greenish blue, and it becomes green and opaque upon exposure. the hardness of this mineral varies from 2.5-3. It is easily soluble in water.

Global Distribution

Krohnkite is a mineral that is found abundantly in Chile. Some of the main locations are as below:

Chile – as large crystals from Chuquicamata, Quetena, west of Calama; Collahuasi, Antofagasts; Incahuasi district, Atacama
England – from wheal Hazard, Cornwall
Hungary – from Recsk copper deposit, Matara mountains
Australia – from Broken Hill, New South Wales.