THE MINERAL HANKSITE
- Chemistry: Na22K(SO4)9(CO3)2Cl, Sodium Potassium Sulfate Carbonate Chloride
- Class: Sulfates
- Uses: Only as mineral specimens
Hanksite is an unusual mineral mostly because of its formula.
It is one of only a handful of minerals that contain both carbonate and sulfate ion groups.
This brings up the question: to what mineral class does it belong?
Some mineral references place it in the carbonates while others put it in with the sulfates.
We have placed it in the sulfate class simply because there are more sulfate groups in its structure than carbonate groups.
Hanksite forms very nice crystals in evaporite deposits.
These evaporite deposits occur in arid environments.
Water, carrying dissolved minerals, floods into a dry lake beds and then just sits.
The arid conditions evaporate the water and concentrate the ions.
When the water is almost gone, crystals start to form.
The mineral halite (salt) is one of the first minerals to crystallize.
As the water becomes even more concentrated, eventually rare and unusual minerals such as
borax or hanksite will crystallize too.
Hanksite crystals can be large and well formed, but are not very complex.
Hanksite makes a good addition to any mineral collection.
- Color is colorless, white, gray, green or yellow; rarely black.
- Luster is vitreous
- Transparency: Crystals are transparent to translucent.
- Crystal System is hexagonal; 6/m 2/m 2/m.
- Crystal Habits include the typical hexagonal dipyramid terminating an hexagonal prism.
The pyramids are often truncated by pinacoids.
The six faces of the pyramids are aligned with the six faces of the prism.
Tabular and twinned crystals are also common.
- Cleavage is perfect in one direction.
- Fracture is uneven.
- Hardness is 3 - 3.5
- Specific Gravity is approximately 2.5 (slightly below average).
- Streak is white.
- Other Characteristics: Has a salty taste, a white powdery film will often cloud crystals and some specimens are
fluorescent yellowish-white under longwave ultraviolet light.
- Associated Minerals are halite,
and other evaporite minerals.
- Notable Occurrences include the type locality of Searles Lake, San Bernardino County as well as Mono Lake, Mono County, California and other evaporite locations.
- Best Field Indicators include crystal habit, taste, occurrences and associations.