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Custom Calcite

Calcite (CaCO3), also known as Iceland spar, is an anisotropic crystal and one of the most birefringent materials available. It is commonly used in polarisers due to this optical property. Calcite transmits at over 75% in the 0.3-2.3µm range making it ideal for the use in visible and NIR applications.

Below is a brief summary of calcite’s optical properties, a full data sheet is available here.

Transmission range

0.3 to 2.3µm

Refractive Index

1.6654 @ 0.51µm


2.71 g/cm3

Melting Point

Decomposes at 825°C


Knoop 155

Mohs 3

Our typical manufacturing specifications are listed below however we are always expanding our capabilities so if your requirements are not mentioned below, please contact our technical sales team who can guide you through your enquiry.


< 5mm to 50mm +

Form error (@633nm)

< 0.25 waves

Centration /parallelism

< 1 arc minute


< 20/10

Typical coatings

BBAR @ 1-2.3µm

Knight Optical supply a range of quality calcite optical components including calcite polarisers and windows, calcite lenses, calcite prisms, and calcite polarisers either from stock or bespoke custom parts made to your specification for a range of applications. Every component is individually tested by our highly skilled technicians in our state of the art metrology lab to ensure all components meet our high quality standards.
Contact our multilingual technical sales team and discover how Knight Optical’s high quality calcite optical components and service can improve your instrumentation and supply chain experience.

Additional Information

  • Birefringence is when there are two distinct refractive indices of a material. This occurs when an unpolarised light beam enters the input surface of the material, it will be split into two polarised beams—the ordinary (o) and extraordinary (e) waves. Calcite’s o-and e-ray refractive indices are 1.6584 and 1.4864 respectively (@590nm).


  • Calcite is very soft so it needs to be handled with care.
  • Calcite is reactive to weak acids and can form carbon dioxide gas.
  • It has a low solubility in water, but it becomes more soluble as the water temperature increases.

Typical Applications

Polarising prisms— laser applications
  • Due to calcite’s transparency in the visible-NIR range and strong birefringence it is an ideal material for polarisers. It can be highly polished to 20/10 scratch/dig on the input and output faces to minimise any scattering.
  • Calcite can withstand high damage threshold and can produce an exceptionally high polarisation purity from the output surface.
  • Common polarising prisms include Rochon, Glan-Taylor/-Glan-Thompson/Glan-laser and Wollaston prisms.
  • As calcite is a birefringent material it can be used to manufacture waveplates to alter the polarising state of the incident light.

Our 2022/2023 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
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