Why does magnesium oxide have different colors

There are many kinds of magnesium oxide, such as light magnesium oxide, heavy magnesium oxide and active magnesium oxide. Different varieties have different colors, including white and light yellow. So what causes the different colors of magnesium oxide?
First is ore. We know that magnesia powder is calcined from ore, so the color of the ore itself determines the color of magnesia powder, which is basically unchangeable.
The second is the production process of magnesium oxide. The color of light magnesium oxide is obviously different from that of heavy magnesium oxide. The light magnesium oxide is white, and the heavy magnesium oxide is slightly yellow. Because heavy magnesium oxide is obtained by calcining ores, while light magnesium oxide is obtained by chemical synthesis. So the color will be white than magnesium oxide.
The third is the main reason: the higher the content of silicon dioxide in magnesium oxide, the whiter the color of magnesium oxide will be. The content of ordinary white magnesium oxide silicon is generally 5.5% - 8%, and the content of yellow magnesium oxide silicon is 2.5% - 4%