Brown-black or brown-red powder/black tetragonal crystals
The color description of manganese tetraoxide varies, mainly related to the morphology, preparation process and observation conditions, and can be divided into the following two categories:
Color under normal conditions
Most authoritative sources describe it as brown-black powder or brown-red powder, which is its most common industrial appearance. For example:
Baidu Encyclopedia (high authority) clearly marks it as "brown-black powder";
Shanghai Nonferrous Network mentions that "brown-red powder" is the form in most cases;
Some manufacturers' information points out that process differences can cause color changes, such as reddish brown or brown-red.
Color of the crystalline state
After crystallization or high-temperature calcination, manganese tetraoxide presents a black tetragonal crystal form, and this description appears consistently in multiple chemical professional sources. For example:
Its spinel structure is a deformed tetragonal system below 1443K, which appears as black crystals at this time;
Chemical Book emphasizes that the black manganese ore (natural Mn₃O₄) in nature is black.
