The Artstor website will be retired on Aug 1st. Abstracts of the Papers Printed in the P... Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London Vol. 1, ...

That is, whatever their original source, upon which point there has been much speculation, they are now found collected in the earth, either free or mixed with other mineral substances.

In some cases they needed a thorough clean. Because each mineral is a unique substance formed of a combination of one or more chemical elements, it was not possible to use the same method to clean ...

Two or more minerals form a rock. A mineraloid is a mineral-like substance that is organic, homogeneous, or naturally occurring. The chemical compositions of mineraloids differ from that of minerals.