Ikaite
Chemical formula: CaCO<sub>3</sub>·6H<sub>2</sub>O
Ikaite is a hydrated calcium carbonate that forms in cold waters and is unstable at room temperature, transforming into calcite.
Properties
- Mohs hardness
- 3
- Luster
- Vitreous
- Streak
- White
- Density
- 1.8
- Cleavage
- Good on {110}
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification The most important diagnostic feature of ikaite is its instability at room temperature. If a crystalline, transparent mineral begins to cloud and decompose upon contact with heat (e.g., a hand) or after being removed from a cold environment, it is most likely ikaite. In field conditions, identification involves finding it in bottom sediments of very cold waters. ## Distinguishing from similar minerals In its natural, cold environment, ikaite may resemble other colorless minerals such as calcite, quartz, or gypsum. However, none of these decompose with a slight increase in temperature. Pseudomorphs after ikaite, i.e., glendonites, are often confused with other minerals, but their characteristic, stellate forms are quite unique. ## Crystal forms Ikaite crystallizes in the monoclinic system, forming pyramidal crystals, often elongated and sharply terminated. It commonly occurs as radial or stellate aggregates, which can reach considerable sizes.
Geological environment
## Genesis Ikaite forms exclusively in aquatic environments with temperatures close to 0°C (typically below 4-6°C). It precipitates from waters rich in calcium and carbonate ions, often in organic sediments on the bottom of seas, lakes, and fjords in polar and subpolar zones. Its formation is often associated with biochemical processes, such as the decomposition of organic matter. ## Mineral associations In its natural environment, ikaite occurs in loose, unconsolidated bottom sediments. After its decomposition, the resulting calcite (in the form of glendonites) co-occurs with clay minerals, pyrite, gypsum, and other sedimentary minerals. ## Locations The most famous occurrence is Ika Fjord in Greenland, where it forms underwater columns. It has also been found in bottom sediments of the Barents Sea, the Sea of Okhotsk, off the coast of Antarctica (Antarctic Peninsula), and in deep, cold lakes. Glendonites, which are pseudomorphs after ikaite, are much more widespread and known, among other places, from Australia, Russia (White Sea coast), USA (Wyoming, California), and Canada.
Rarity
Extremely rare
For collectors
## Quality criteria The quality of an ikaite specimen is almost exclusively defined by its existence. Any preserved, stable (under refrigeration) crystal or aggregate is an extraordinary rarity. Large, well-formed, transparent crystals or aesthetic, stellate aggregates would be most highly valued. Since specimens are practically unavailable on the market, these criteria are purely theoretical. ## Popular localities The only source of potential collector specimens is the type locality in Ika Fjord in Greenland. Obtaining material from there and transporting it in a frozen state is logistically extremely difficult and costly, which means that specimens in private collections are virtually non-existent.
Care and storage
## Cleaning Ikaite specimens are extremely sensitive and practically impossible to clean using standard methods. Any contact with room-temperature water or even warming in the hand will cause it to decompose. The specimen must be kept at a constant, low temperature. ## What to avoid Temperatures above 0-4°C must be strictly avoided. Heating leads to irreversible dehydration and transformation into calcite powder or an amorphous mass. Acids, which rapidly dissolve it, and any chemicals should also be avoided. ## Storage The only effective storage involves keeping the specimen in a freezer or cold storage at sub-zero temperatures, preferably in an airtight container to prevent sublimation. Display is only possible in specialized, refrigerated showcases.