Germanium – used for lenses, mirrors, windows & prisms


Symbol: Ge

Atomic Number: 32

Atomic Weight: 72.64

Classification: Metalloid

Phase at Room Temperature: Solid

Density: 5.323 grams per cm cubed

Melting Point: 938°C, 1720°F

Boiling Point: 2833°C, 5131°F

Discovered by: Clemens Winkler in 1886


 What is Germanium

It is the third element of the fourteenth column of the periodic table. It is classified as a metalloid and is similar in properties to the other metalloids near it in the periodic table which are silicon and arsenic. Ge atoms have 32 electrons and 32 protons with 4 valence electrons in the outer shell.

 Under standard conditions Germanium is a hard, shiny, silvery-grey solid that is very brittle. It is one of the few elements that expands when it freezes or turns solid. As a metalloid, it has both metal and non-metal qualities. It also is a semiconductor, which means it has electrical conductivity between an insulator and a conductor. This characteristic has led to it being used in electronics.

 Germanium does not react with oxygen at room temperature but will form germanium dioxide at higher temperatures. Most germanium used by industry is produced in China as a by-product of mining sphalerite zinc ore, where it is found in small traces.

It was discovered by Clemens Winkler who found the element in the mineral argyrodite in 1886 and named it after his home country Germany.



 What is Germanium used for?

The majority of germanium is used in optical systems. This is because Germania (GeO2) has good qualities for working with light and lasers. It is used in applications like cameras, fibre optics, and microscopes, and infrared optics.

  • Camera Lenses – used in the manufacture of wide-angle camera lenses. It gives special properties to the glass.
  • Alloys –  it can be useful to add to other metals.
  • Fluorescent Lamps – it is one of the elements on the inside of the fluorescent bulbs.
  • Chemotherapy – scientists are studying germanium for use in chemotherapy to help treat cancer.
  • Bacteria – some compounds that include germanium are useful in killing bacteria while not harming animals.
  • Electronics – it can be combined with silicon to make silicon germanium (SiGe), solar cells, and some metal alloys.
  • Plastics – it is also used as a catalyst to produce some types of plastics.


Germanium Optics

Ge in the range of 2-12μm is the most commonly used material in the production of spherical lenses and windows for high efficiency infrared in the imaging system operating in both 3-5 and 8-12μm.

Its wide transmission range and visible opacity make it highly suitable for IR laser applications. It also acts as a long pass filter for wavelengths greater than 2 µm. In addition, germanium is inert to air, water, alkalis, and many acids. The high refractive index and minimal surface curvature of Ge are perfect for manufacturing low-power imaging systems.  

Germanium is extremely sensitive to temperature, and absorption is so large that it is nearly opaque at 100 °C and completely non-transmissive at 200 °C.

 When handling optics, always wear gloves. This is especially true when working with germanium, as dust from the material is hazardous. For your safety, please follow all proper precautions, including wearing gloves when handling these windows and thoroughly washing your hands afterward.


Germanium from Global Optics

Lenses – optical lenses made of polished germanium. These lenses are rugged and resistant to corrosion, and are ideal for harsh environments and applications where there is constant exposure to the elements.

Windows –  an optical window which is opaque to UV and visible light but has a broad transmission range in IR.


Global Optics also offer Germanium prisms, germanium filters, germanium mirrors and germanium optics.

If you’re looking for Germanium glass, you can rest assured that our products will provide you with the best value for money. Our highly skilled technicians ensure all components meet our high quality standards and our germanium products have a high precision rate and can be customised to suit your needs specifically.