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Macor is the trademark for a machineable glass-ceramic developed and sold by Corning Inc. It is a white material that looks somewhat like porcelain. Macor is a good thermal insulator, and is stable up to temperatures of 1000 °C, with very little thermal expansion or outgassing. It can be machined into any shape using standard metalworking bits and tools.[1]


Macor is made up of fluorphlogopite mica in a borosilicate glass matrix. Its composition is roughly:


Macor has a density of 2.52 g/cm3, and a thermal conductivity of 1.46 W/(m·K). Its low-temperature (25 to 300 °C) thermal expansion is 9.3×10−6 m/(m·K). Its compressive strength is 50×103 lb/in2 (~350 MPa). Nominal engineering properties are comparable to borosilicate glass.[2]

Macor comes in a standard size maxi slab (36x6cm approx.) Corning Macor Maxi-Slab.[3] Components, bars, rods and plates can be machined within the size of this slab (hand tools can be used).


There are no major safety concerns or toxic effects associated with Macor. The dust created when machining it can be an irritant and inhalation should be avoided.[4]