GYPSUM POP – Your search for quality minerals ends here
GYPSUM POP

GYPSUM POP

Chemistry: CaSO4-2(H2O), Hydrated Calcium Sulfate
Class: Sulfates
Uses: plaster, wall board, some cements, fertilizer, paint filler, ornamental stone, etc

Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.

Gypsum has several variety names that are widely used in the mineral trade.

  • “Selenite” is the colorless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.
  • Another variety is a compact fiberous aggregate called “satin spar” . This variety has a very satin like look that gives a play of light up and down the fiberous crystals.
  • A fine grained massive material is called “alabaster” and is an ornamental stone used in fine carvings for centuries, even eons.

Crystals of gypsum can be extremely colorless and transparent, making a strong contrast to the most common usage in drywall. The crystals can also be quite large. Gypsum is a natural insulator, feeling warm to the touch when compared to a more ordinary rock or quartz crystal. Sheets of clear crystals can be easily peeled from a a larger specimen.

Gypsum crystals can be extremely large – among the largest on the entire planet. A cave in Naica, Mexico contains crystals that dwarf the people inside. Apparently, ideal conditions for the slow growth of gypsum were maintained for thousands of years, allowing a few crystals to grow to enormous sizes.

Plaster of Paris is made by heating gypsum to about 300 degrees Fahrenheit, driving 75% of the water out of the mineral. This reaction absorbs energy, enabling a sheet of drywall to resist fire for a while. Heating further to about 350 degrees F drives out the remaining water and results in conversion to the mineral anhydrite.

PHYSICAL CHARACTERISTICS:

  • Color is usually white, colorless or gray, but can also be shades of red, brown and yellow.
  • Luster is vitreous to pearly especially on cleavage surfaces.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include the tabular, bladed or blocky crystals with a slanted parallelogram outline. The pinacoid faces dominate with jutting prism faces on the edges of the tabular crystals. Long thin crystals show bends and some specimens bend into spirals called “Ram’s Horn Selenite” Two types of twinning are common and one produces a “spear head twin” or “swallowtail twin” while the other type produces a “fishtail twin”. Also massive, crusty, granular, earthy and fiberous.
  • Cleavage is good in one direction and distinct in two others..
  • Fracture is uneven but rarely seen.
  • Hardness is 2 and can be scratched by a fingernail.
  • Specific Gravity is approximately 2.3+ (light)
  • Streak is white.
  • Other Characteristics: thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it’s use in drywall as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
  • Best Field Indicators are crystal habit, flexible crystals, cleavage and hardness.

The term plaster can refer to plaster of Paris (also known as gypsum plaster), lime plaster, or cement plaster. This article deals mainly with plaster of Paris / gypsum plaster.

Plaster of Paris is a type of building material based on calcium sulphate hemihydrate, nominally CaSO4·1/2H2O. It is created by heating gypsum to about 150 °C.[1]

2 CaSO4·2H2O → 2 CaSO4·0.5H2O + 3 H2O (released as steam).

A large gypsum deposit at Montmartre in Paris is the source of the name.[1][2] When the dry plaster powder is mixed with water, it re-forms into gypsum. Plaster is used as a building material similar to mortar or cement. Like those materials plaster starts as a dry powder that is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after drying, and can be easily manipulated with metal tools or even sandpaper. These characteristics make plaster suitable for a finishing, rather than a load-bearing material.

Plaster was a common building material for wall surfaces in a process known as lath and plaster, whereby a series of wooden strips on a studwork frame was covered with a semi-dry plaster that hardened into a surface. The plaster used in most lath and plaster construction was mainly lime plaster, with a cure time of about a month. To stabilize the lime plaster during curing, small amounts of Plaster of Paris were incorporated into the mix. Because Plaster of Paris sets quickly, “retardants” were used to slow setting time enough to allow workers to mix large working quantities of lime putty plaster. A modern form of this method uses expanded metal mesh over wood or metal structures, which allows a great freedom of design as it is adaptable to both simple and compound curves. Today this building method has been partly replaced with drywall, also composed mostly of gypsum plaster. In both these methods a primary advantage of the material is that it is resistant to a fire within a room and so can assist in reducing or eliminating structural damage or destruction provided the fire is promptly extinguished.

One of the skills used in movie and theatrical sets is that of “plasterer”, and the material is often used to simulate the appearance of surfaces of wood, stone, or metal. Nowadays, plasterers are just as likely to use expanded polystyrene, although the job title remains unchanged.

Address 1: H.K Microns 23, Punjabi Bagh, Indore | Address 2: H.K Microns, Balicha, Udaipur
Copyright © 2020 HK Microns. All rights reserved- Designed By Casa Informatix