Gypsum

Gypsum is moderately water-soluble (~2.0–2.5 g/L at 25 °C) and, in contrast to most other salts, it exhibits a retrograde solubility, becoming less soluble at higher temperatures. When the crystal lattice is heated it loses liquid water molecules to evaporation and thus gains solidity. As for, its solubility in saline solutions and in briness is also strongly dependent on Naclconcentration.

Category:                                  Sulphate minerals

Chemical formula:                  CaSO₄·2H₂O

Crystal symmetry:                 Monoclinic 2/m

Color:                                   Colorless to white; may be yellow, tan, blue, pink, brown, reddish

                                            brown or gray due to impurities

Crystal habit:                         Massive, flat. Elongated and generally prismatic crystals

Crystal system:                      Monoclinic 2/m – Prismatic

Cleavage:                              Perfect on {010}, distinct on {100}

Fracture:                              Conchoidal on {100}, splintery parallel to [001]

Tenacity:                              Flexible, inelastic.

Mohs scale hardness:           1.5–2 (defining mineral for 2)

Luster:                                Vitreous to silky, pearly, or waxy

Streak:                               White

Specific gravity:                  2.31–2.33

Optical properties:              Biaxial (+)

Refractive index:                     n_α = 1.519–1.521
                                                   n_β = 1.522–1.523
                                                   n_γ = 1.529–1.530

Solubility:                             Hot, dilute HCl

Gypsum can be found in Sokoto, Ogun, Gombe, Cross- Rivers,  Kogi, Benue and Ebonyi states

Generally, the process involves quarrying, blasting, crushing and milling.  This project is expected to concentrate on grinding operations.

Gypsum ore, from quarries and underground mines, is crushed and stockpiled near the plant.  As needed, the stockpiled ore is further crushed and screen to about 5.0 millimeters (2inches) in diameter.  If the moisture content of the mined ore is greater than 0.5 weight percent, the ore must be dried in a rotary dryer or heated in a roller mill.  Ore dried in a rotary dryer is conveyed to a roller mill, where it is ground to a mesh size of less than 149 micrometer (MM) or (100 mesh size).  The ground powders are now bagged for sale.

The production of gypsum has been on the increase in most part of the world.  This is probably due to the increase in industrial activities of the world economy which has just recovered from the global recession.  In addition, the rapid increase in housing initiatives and the provision of infrastructure for the increasing population, require the utilization of cement as major input.  The direct impact of all these, is the sharp increase in the demand for gypsum globally.

At present, the largest users of gypsum in Nigeria are manufacturers of cement.  A combined total gypsum requirement by the existing cement plants is  about 182,000 MT.

There is also a strong demand for gypsum for chalk, ceramic moulds, and medical use in the form of Plaster of Paris.  Local supply has been by small-scale miners whose production is inadequate and limited by their small scale capacities.  This leaves a large unsatisfied market for this industrial filler.

Gypsum is an important input for the production of cement. It is also used for the production of Plaster of Paris (P0P) and classroom chalk, etc.  With a population estimated at over one hundred and sixty million {160,000,000} growing at a rate of 3.5% per annum has a short fall in the supply of housing units that as been estimated to be between 16 – 17 million, Nigeria has a growing and sustainable market for cement and plaster of Paris {POP}

Current cement production is put at 8 million tones per annum while the national requirement is 9.6 million tones. About one billion tones of gypsum deposits are spread over many states in Nigeria.  Being a key input in cement production, a strategy for large scale mining gypsum is urgently required to sustain existing cement plants and meet future expansion.