Mäkinenite
Chemical formula: NiSe
Mäkinenit is a rare nickel selenide, forming small, hexagonal crystals with a metallic luster, found in sulfide deposits.
Properties
- Mohs hardness
- 2.5-3
- Color
- Yellow
- Luster
- Metallic
- Streak
- (not reported)
- Density
- 0
- Cleavage
- (not reported)
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of mäkinenit under amateur conditions is practically impossible. This mineral occurs as microscopic inclusions in other sulfides and requires specialized techniques for recognition, such as ore microscopy (reflected light analysis) and chemical analysis using an electron microprobe (EDS/WDS) to confirm its composition (presence of nickel and selenium). ## Distinguishing from Similar Minerals Under the microscope, it can be confused with other fine, metallic minerals such as pentlandite, pyrite, chalcopyrite, or other selenides. Differentiation relies on subtle differences in color and reflectivity, and final confirmation requires chemical analysis. ## Crystal Forms It forms small, hexagonal or trigonal crystals, often tabular or platy in habit. It typically occurs as irregular grains or inclusions within other minerals.
Geological environment
## Genesis Mäkinenit is a hydrothermal mineral, associated with nickel and copper sulfide deposits. It forms under low-temperature conditions, crystallizing from selenium-rich solutions. It is one of the later minerals in the crystallization sequence in such deposits. ## Mineral Associations It most commonly co-occurs with pentlandite, in which it forms characteristic inclusions. It is also accompanied by chalcopyrite, karelianite, clausthalite, cuproselenide, umangite, eskebornite, ferroselite, pyrite, pyrrhotite, as well as platinum-group minerals (PGM). ## Localities The most important and best-documented occurrences of this mineral are: - **Finland** - Kuusamo deposit (type locality). - **Canada** - Thompson area in Manitoba and the Hope deposit
Rarity
Very rare
For collectors
## Quality Criteria As a microscopic mineral, mäkinenit is not collected for aesthetic purposes. Its collector's value is purely scientific and systematic. The most valuable specimens are those (usually polished microscopic sections) with analytically confirmed presence of mäkinenit, originating from the type locality (Kuusamo, Finland) or other classic occurrences. ## Popular Localities By far, the most prized specimens come from the type locality in Kuusamo, Finland. Material from Canadian deposits in Thompson (Manitoba) and Hope
Care and storage
## Cleaning Due to the extreme rarity and small size of the crystals, which are typically intergrown with other minerals, mechanical cleaning is neither recommended nor practical. Specimens should be left undisturbed. ## What to Avoid Contact with chemicals, especially acids, which can react with sulfides and selenides, should be avoided. Ultrasound and sudden temperature changes should also be avoided. As a brittle mineral, it is susceptible to mechanical damage. ## Storage Specimens containing mäkinenit, typically polished sections or rock fragments, should be stored under stable conditions, in padded collector's boxes, away from dust, moisture, and chemicals. It is best to store them in a dry environment to prevent potential oxidation.