At the final stage of the harvesting process, the harvester module slightly compresses the extruded material, sometimes causing the solid starch to transform into helioquid.
"Isotopes and variants have different levels of purity. The more pure this strange mineral is, the more common minerals can be recycled from it. Purity levels range from PL-10 to PL-90."
Note that variants appear randomly, during the exploitation of common minerals. There's no way to detect them directly.