Platinum is the precious metal used to manufacture laboratory crucibles. Its exceptional chemical inertness means it resists attack by many acids, molten salts, and other aggressive substances that would corrode ordinary containers.
Platinum also withstands very high temperatures without readily oxidizing or contaminating a sample. That combination makes platinum crucibles valuable in gravimetric analysis, fusion methods, thermogravimetric analysis, and X-ray fluorescence sample preparation. The metal is dense and malleable, so it can be formed into thin, durable laboratory vessels.
The answer is not simply “any noble metal.” Gold can resist some chemical reactions but is relatively soft and can react with or alloy with substances used in high-temperature work. Silver has a lower melting point and is more chemically reactive, while palladium is not the standard answer for general laboratory crucibles. Platinum alloys, including platinum-rhodium compositions, are also used for specialized applications, but the canonical answer to this question is platinum.
Historically, the first platinum crucible is credited to Franz Karl Achard in 1784. Because platinum equipment is expensive, laboratories often use porcelain, nickel, glass, or ceramic alternatives when the sample and temperature allow them.