Silicon Oxide (SiO2 )
Silicon oxide is resistant to most acids and bases. It is only attacked by HF acid. Because it is electrical insolating, it is used in the semiconductor industry as barrier layer. Since it is transparent to light, it is used for optical purposes.
The melting point lies at 1700°C. However, it is only stable in an oxygen atmosphere. In vacuum around 900°C the SiO2 is converted to SiO and oxygen. The former is a gas and will cause the SiO2 sublimate.