Colloidal minerals are molecules of minerals suspended in a liquid. The particles are not dissolved and may carry an electrical charge which enables them to combine with another particle to make a compound and precipitate out as a solid. These electrically charged particles are not the same thing as ions or cations which are electrically charged atoms or molecules.
Most colloidal minerals are clay dissolved in water. Depending on the source of clay, it may contain toxic minerals like aluminum or lead.
I have searched medical research and found nothing that suggests colloidal minerals are more or less absorbable than mineral supplements in pills. In fact, I have not seen any research on absorption of colloidal minerals after checking what is available in a Medline search and many nutrition reference texts. To that conclusion, I deemed the information about colloidal minerals to be from testimonials, not research.