Haapalaite
Chemical formula: 2[(Fe<sup>2+</sup>,Ni<sup>2+</sup>)S<sup>2-</sup>]·1.61[(Mg,Fe<sup>2+</sup>)(OH)<sub>2</sub>]
Haapalaite is a very rare iron, nickel, and magnesium sulfide, characterized by a brown color, metallic luster, and platy habit.
Description
## Characteristics Haapalaite is a mineral with a metallic luster and a characteristic brown or brownish-yellow color. It typically occurs as small, hexagonal flakes or platy aggregates disseminated in the host rock. Its structure is layered, giving it a mica-like appearance, and individual flakes are flexible. ## Physical Properties This mineral is extremely soft, with a Mohs hardness of only 1, meaning it can be scratched with a fingernail. It possesses perfect, unidirectional cleavage, allowing it to easily split into thin, flexible lamellae. It is opaque, and its density is approximately 3.11 g/cm³. ## Colors and Varieties Its typical color is brown to brownish-yellow. There are no named color varieties or commercial names. ## History and Name The mineral's name, given in 1972, honors Paavo Haapala (1906–2002), a Finnish geologist and exploration director at Outokumpu Oy. It was discovered and described based on material from Kokka, Finland. ## Uses Due to its rarity and occurrence in small quantities, haapalaite has no industrial applications. It is solely an object of scientific and collecting interest.
Diagnostic features
## Identification Key diagnostic features of haapalaite are its extreme softness (Mohs hardness 1), perfect cleavage into flexible lamellae, metallic luster, and brown color. Its occurrence in serpentinites is also characteristic. ## Distinguishing from Similar Minerals It can be confused with other platy minerals. It is distinguished from mica group minerals (e.g., biotite) by its metallic luster, black streak, and higher density. It is visually almost identical to valleriite, and their definitive differentiation often requires advanced analyses (e.g., X-ray). Pentlandite, with which it co-occurs, is significantly harder (3.5-4). ## Crystal Forms Haapalaite most commonly forms small, hexagonal flakes or plates. It occurs as disseminated platy and granular aggregates in the host rock. Well-formed, isolated crystals are extremely rare.
Geological environment
## Genesis Haapalaite forms as a result of serpentinization processes of ultramafic igneous rocks, such as dunites and peridotites. It is a product of low-temperature hydrothermal alterations. ## Mineral Associations This mineral often co-occurs with pentlandite, maucherite, chromite, magnetite, millerite, valleriite, and serpentine group minerals. ## Localities The most important haapalaite localities worldwide include the type locality in Kokka and deposits in the Outokumpu region in Finland. It is also known from the nickel-bearing complex in Norilsk (Russia), from several locations in Canada (Quebec, Ontario), and from Zimbabwe.
Rarity
Very rare
Collector aspects
## Quality Criteria The collector's value of haapalaite specimens primarily depends on the abundance of mineral aggregates in the host rock and the size of individual flakes. Samples with visible, well-formed hexagonal crystal outlines are prized. Association with other rare minerals is also important. ## Popular Localities The most classic and valued specimens, often serving as reference material, come from Finland, especially from the type locality in Kokka and from mines in the Outokumpu region.
Care and storage
## Cleaning Haapalaite is extremely soft and delicate. To remove dust, use only a very soft, dry brush. Do not use water, ultrasonic cleaners, or any chemical agents. ## What to Avoid Avoid any physical contact that could scratch or abrade the mineral. It is sensitive to pressure, which causes it to delaminate. As a sulfide, it may be susceptible to oxidation in humid environments, so it should be protected from moisture and sudden temperature changes. ## Storage Haapalaite specimens are best stored in a closed, padded "micromount" box to protect them from mechanical damage, dust, and moisture. Display should occur under stable environmental conditions.