Sakhaite
Chemical formula: Ca<sub>48</sub>Mg<sub>16</sub>(BO<sub>3</sub>)<sub>32</sub>(CO<sub>3</sub>)<sub>16</sub>·2(H<sub>2</sub>O,HCl)
Sakhait is a rare calcium and magnesium borate-carbonate, most often forming spherical or granular aggregates of white color.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous to Greasy
- Streak
- White
- Density
- 2.78 - 2.82
- Cleavage
- None
- Fracture
- Conchoidal to Uneven
- Transparency
- Translucent to Opaque
- Crystal system
- Cubic
Diagnostic features
## Identification A characteristic feature of sakhait is its violent reaction (effervescence) with hydrochloric acid, which is typical for carbonates. Its occurrence as spherulites or granular masses in skarns is also an important clue. Its hardness (5) distinguishes it from many other carbonates, such as calcite (3). ## Distinguishing from Similar Minerals Sakhait can be confused with other white, massive minerals from skarns, such as calcite, dolomite, or wollastonite. Its higher hardness distinguishes it from calcite and dolomite. It can be distinguished from wollastonite and other silicates by the acid reaction test. However, precise identification requires advanced methods, such as X-ray diffraction (XRD). ## Crystal Forms Sakhait crystals are rare and usually very small (up to 1-2 mm). They adopt forms typical of the isometric system, such as cubes and octahedra. The most common forms of occurrence are granular aggregates, massive forms, and spherical spherulites.
Geological environment
## Genesis Sakhait is a mineral typical of magnesian skarns. It forms in the contact zone of granitoid intrusions with carbonate rocks (limestones and dolomites), under conditions of relatively high temperature and low pressure. It is a product of metasomatism, a process of chemical alteration of rocks under the influence of hot, boron-rich solutions. ## Mineral Associations This mineral often co-occurs with other borate and skarn minerals. Its typical associations include kotoite, ludwigite, fluoborite, szaibelyite, as well as calcite, dolomite, magnetite, spinel, and minerals from the humite group. ## Localities The most important and classic sakhait localities are in Russia, in Yakutia (Sakha Republic), from which its name originates (Titovskoye, Dokunnanskoye, Efkanskoye deposits). It is also known from several other locations worldwide, including Hol Kol mine in North Korea, Nandan mine in China, and Clark County in Nevada (USA).
Rarity
Rare
For collectors
## Quality Criteria The most valued by collectors are specimens with well-formed, even if small, crystals of regular shapes (cubes, octahedra). Well-formed spherulites with a distinct, radial structure are also highly prized, especially if they contrast with the rock matrix. Purity and white color without undesirable discolorations also increase the specimen's value. ## Popular Localities Specimens from the type locality in Yakutia (Russia) have the greatest historical and scientific significance. Spherulitic aggregates from China (Nandan mine) also appear on the collector's market.
Care and storage
## Cleaning Sakhait specimens should be cleaned very carefully, preferably dry, using a soft brush to remove dust. Due to its reactivity with acids, contact with water should be avoided, especially if it is not distilled, as it may contain dissolved CO₂, forming weak carbonic acid. ## What to Avoid Sakhait is sensitive to acids – it reacts violently with hydrochloric acid, releasing carbon dioxide. It should be protected from all chemicals, as well as from moisture. It should not be exposed to prolonged strong light or extreme temperatures. ## Storage It is recommended to store sakhait in a dry place, preferably in a closed, padded display box or cabinet, to protect it from dust, moisture, and mechanical damage. A good practice is to keep it away from sulfide minerals, which can weather and create an acidic environment.