Here's why:

* Silicates are compounds containing silicon and oxygen, usually in the form of the SiO₄⁴⁻ anion. They are the most abundant group of minerals on Earth.

* Antimony is a metalloid element, meaning it has properties of both metals and nonmetals. It doesn't contain silicon or form silicates.

Some common antimony compounds include:

* Stibnite (Sb₂S₃): A sulfide mineral of antimony.

* Valentinite (Sb₂O₃): An oxide mineral of antimony.

Let me know if you have any more questions about minerals!