Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

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AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...
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What is Calcite and types of calcite and its uses

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What is Calcite and types of calcite and its uses 

 Calcite is an open-source software framework that provides a SQL parser, validator, and optimizer. It is designed to be integrated into other software applications, allowing them to support SQL queries and operations. It was developed by the Apache Software Foundation and is written in Java. Calcite is commonly used in big data and analytics applications to enable SQL access to different data sources and formats.

Types of Calcite

Calcite is a carbonate mineral that is widely used in various industries. Below are some of the types of calcite:

  • Optical Calcite: Also known as Iceland Spar, this type of calcite is transparent and has the ability to split light into two rays.
  • Rhombic Calcite: This type of calcite has a rhombus shape and is commonly found in sedimentary rocks.
  • Scalenohedral Calcite: This type of calcite has a scalenohedral shape and is commonly found in hydrothermal veins.
  • Dolomite: Although not technically a type of calcite, dolomite is closely related to calcite and is composed of calcium magnesium carbonate.

Details of Types of Calcite

Each type of calcite has unique properties and characteristics. Below are some of the details of each type of calcite:

Type of CalciteColorCrystal System
Optical CalciteColorless, white, gray, yellow, orange, and redTrigonal
Rhombic CalciteColorless, white, yellow, and redRhombohedral
Scalenohedral CalciteColorless, white, gray, yellow, and brownTrigonal
DolomiteColorless, white, pink, gray, and brownTrigonal

Elementary Entry Chemical Analysis

The chemical formula for calcite is CaCO3. Below is the elementary entry chemical analysis for calcite:

  • Calcium (Ca) - 40.04%
  • Carbon (C) - 12.00%
  • Oxygen (O) - 47.96%

Use of Calcite

Calcite is commonly used for various purposes, including:

  • Construction and building materials
  • Manufacturing of cement and concrete
  • Production of lime
  • In the production of glass and ceramics
  • In metallurgical processes
  • As a neutralizer in the chemical industry
  • As a soil conditioner in agriculture
  • In the production of pharmaceuticals and cosmetics

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