This is easier understood if you picture a basketball in your mind and imagine the amount of surface around the outside. Now imagine if that basketball were filled with small marbles. If you measured all the surface around each marble it would be many times greater than that around the big basketball. The amount of surface of a mineral particle is important since the body attacks and breaks down minerals by attaching to their surface. The greater the surface the greater the absorption, hence the smaller the particle the greater the potential for absorption.
Colloids are very small particles that suspend in liquids such as water.
These particles contribute to overall absorption due to the immense surface the body has available to acidify and break them down. The pH scale runs from 0 through 14. The mid point, number 7 is neutral. Everything lower than 7 is acidic and everything higher than 7 is alkaline. In order for minerals to be properly absorbed, they need to be acidic.