Difference Between Calcite and Halite

The key difference between calcite and halite is that calcite is the mineral form of calcium carbonate, whereas halite is the mineral form of sodium chloride.

Calcite and halite are mineralogical names. These are common minerals that are useful for the production of different compounds. Although the names sound similar, they are very distinct minerals of different compositions, thus, different chemical and physical properties.

1. Overview and Key Difference
2. What is Calcite
3. What is Halite
4. Side by Side Comparison – Calcite vs Halite in Tabular Form
5. Summary

What is Calcite?

Calcite is the mineral form of calcium carbonate. It is the most stable polymorph of calcium carbonate. Hence, it is a carbonate mineral. Its crystal system is trigonal. Moreover, it is mainly colourless or white, but sometimes it occurs in different colours like grey, yellow or green as well, depending on the composition. The lustre of this mineral is vitreous to pearly on cleavage surfaces while the mineral streak is white.

Calcite mineral has a considerable hardness; its Mohs hardness value is 3. The specific gravity of calcite is 2.71. Moreover, this mineral occurs as either transparent or opaque. Occasionally, it may show phosphorescence or fluorescence. Furthermore, single crystals of calcite show birefringence; if we observe an object through this crystal, it appears doubled.

Apart from that, calcite can dissolve in many acid forms. Similarly, it can dissolve in groundwater. Sometimes, it gets precipitated by groundwater; however, factors like temperature and pH of the groundwater have an effect on this precipitation. Moreover, the construction industry is the main consumer of calcite; they use this mineral in the form of limestone and marble to produce cement and concrete. In addition to these, the microbiologically precipitated calcite has many applications including soil remediation, soil stabilization and concrete repair.

What is Halite?

Halite is the mineral form of sodium chloride. The common name for this mineral is rock salt. Its chemical formula is NaCl. Halite is the mineralogical name. Typically, this mineral is colourless or white. But, sometimes, it may have a colour such as light blue, dark blue, purple, pink, red, orange, yellow or grey. This is because the colour can vary due to the presence of impurities along with sodium chloride.

Since the chemical formula of the repeating unit of halite is NaCl, the formula mass is 58.43 g/mol. It has a cubic crystal structure. The mineral is brittle, and the mineral streak is white. When considering the occurrence of this mineral, it exists in vast beds of sedimentary evaporites. These evaporites are created due to the drying of lakes, seas, etc.

The most important use of this salt is managing ice. Brine is a solution of water and salt. Since brine has a lower freezing point compared to pure water, we can put brine or the rock salt on ice (at 0°C). This will cause the ice to melt. Hence, in cold climates, people spread this salt in their sidewalks and driveways to melt the ice as a de-icing agent.

What is the Difference Between Calcite and Halite?

Calcite and halite are mineralogical names. The key difference between calcite and halite is that the calcite is the mineral form of calcium carbonate, whereas the halite is the mineral form of sodium chloride. Therefore, the chemical formula for calcite is CaCO3 and chemical formula of halite it is NaCl. Also, when considering the appearance, calcite occurs in different colours like grey, yellow or green, whereas the halite usually occurs in different colours such as light blue, dark blue, purple, pink, red, orange, yellow and grey. Furthermore, another significant difference between calcite and halite is that the crystal system of calcite is trigonal while the crystal system of halite it is cubic.

Summary – Calcite vs Halite

Reference:

1. “Halite.” Wikipedia, Wikimedia Foundation, 20 Sept. 2019, Available here.

Image Courtesy:

1. “Calcite-Mottramite-cktsu-45b” By Rob Lavinsky, iRocks.com (CC-BY-SA-3.0) via Commons Wikimedia
2. “Halit (NaCl) – Kopalnia soli Wieliczka, Polska” By Lech Darski – Own work (CC BY-SA 4.0) via Commons Wikimedia