#MineraloftheMonth

Posted on: March 30, 2022 | National Museum of the Philippines

For today’s feature, let us talk about a mineral with a thousand uses – Bentonite.

Bentonite is a naturally-occurring material made essentially of clay minerals belonging to the smectite group. These clay minerals are hydrous aluminum silicates composing iron and magnesium and either sodium or calcium. Most bentonites are formed when minute glassy materials derived from volcanic ashes are decomposed after intense contact with water.

It is a plastic material that swells or shrinks in response to either the addition or removal of water respectively. And it has an incredible ability to expand up to 14 times its original volume when coming into contact with water, creating a gelatinous and viscous substance.

Do you know that bentonite occurs in rocks that were deposited about 488.3 to 2.6 million years ago (Ordovician to Neogene)? The formation of a large volume of deposit of bentonite requires rather special geologic conditions.

Owing to its structure, small crystal size, chemical composition, and exchangeable ions, bentonite has several unique properties. These include large chemically active surface area, unusual hydration characteristics, ability to modify considerably the flow behavior of liquids, strong colloidal properties, high viscosity, water absorption, and many more. These are the reasons for its wide range of applications.

Bentonite is an important mineral commodity used in several industries. Locally produced and processed bentonites are used as additives, grouting, binders in foundry sand, and filler in animal feeds. It is also used to seal dams, as drilling muds, in Portland cement and concrete, insecticides, soaps, pharmaceuticals, paints, in the manufacture of paper, and many more! Plus, it’s also already entered the world of skincare as its natural properties are said to be beneficial for our skin.

This important resource offers a thousand benefits and applications. With our advancing technologies, we are also taking advantage of this wonderful mineral. Visit us and see for yourself this mineral along with our other mineral collections.

Text and image by the NMP Geology and Paleontology Division