Mineral collectors will probably have specimens
where one mineral occurs inside the crystal
or crystals of another, the "host" mineral.

These specimens, either in hand or micro-crystal size,
can be both fascinating and aesthetic.

Additionally, they may also have a scientific value.
A comrehensive study of inclusions may help to decipher
the sequence of mineralization of a mineral deposit.

Perhaps, the best-known and most aesthetic example
of a mineral inclusion is that of rutilated quartz
- where golden, yellow or brown needles of rutile
(titanium oxide) occur within the quartz.

Indeed, common quartz frequently may contain
inclusions of a wide variety of other species.

In extreme instances, inclusions may be so concentrated
as to colour the host mineral species a rather less than typical colour.

QUARTZ - with dark green chlorite inclusions.
Dingle Peninsula, Co. Kerry, REPUBLIC of IRELAND. (crystals to 3cms).

The purple variety of quartz, amethyst, is coloured by iron impurities. These are inclusions not normally detected by the human eye. Citrine quartz is a similar example.

Smoky quartz can be so coloured by inclusions, but this colouration is often caused by the natural radiation of radioactive minerals adjacent to the quartz.

Quartz can be found in several other colours.

Green quartz is sometimes referred to as aventurine quartz. In this case, flecks of green muscovite have infused the quartz to impart the colour. These are inclusions which are so small that they cannot be detected by the naked eye.

Similarly, green quartz can also be the result of chlorite, actinolite and hedenbergite inclusions. In these cases, the inclusions of these minerals in the quartz may be detected visually.

QUARTZ: Amethyst variety. - Angus, Scotland.
Cavity infilled with a clear chalcedony rind and inner zones
of white quartz and purple amethyst.

Domeno, SPAIN

Red quartz is normally the result of iron mineral inclusions or impurities.
The example above shows quartz with inclusions of iron rich clay.

The photo to the right shows an example of a single, platy hematite crystal
as an inclusion in clear quartz.

Quartz with hematite crystal inclusion.
Florence Mine, Cumbria, England.

SMOKY QUARTZ - Brazil.
The colour of smoky quartz
is often caused by natural radiation.

Phantoms - Zoning

Phantom or "ghost" crystals may be coated by another mineral species on their surface, highlighting the "ghost" form within the larger crystal after its regrowth.

A similar example is colour zoning, where a crystal re-growth at a later stage occurs with or without the inclusions or trace elements of the previous growth phase.

The photo on the right shows such an example.
The lower portion of the clear quartz crystal has an internal "phantom" crystal. This is particularly evident because at the end of the previous growth phase of the quartz crystal,
a layer of greenish chlorite coated its surface.

Gem Inclusions

In gemmology, mineral inclusions in cut and faceted gemstones can be useful as a type of "security ID system", giving a particular gemstone a unique "inclusions signature" that distinguishes it from others.

Indeed, a database exists of such inclusions in gemstones
for this purpose alone.

Quartz - Ambatofinandrahana, MALAGASY.
Quartz crystal with a chlorite-coated, internal, phantom crystal.

This is the case with some gemstones, such as topaz,
and also with quartz, where techniques are employed to alter or enhance their natural colour.

Blue quartz is often regarded to be the result
of trace flecks of gold within the quartz.

True or false, "aqua" blue quartz, though very distinguished in appearance, is usually the result of human intervention.

Naturally occuring blue quartz is very uncommon,
despite the occurence of numerous, fairly common,
blue-coloured minerals in Nature.
The photo on the right shows such an example.

The colour, in this case, is due to inclusions of the rare silicate mineral, aerinite, which is found normally occuring as massive coatings of a blue or blue-grey colour.

Blue QUARTZ - Málaga province, Andalucía, SPAIN.

Multiple Mineral Inclusions

The panel of photos below show the variations
and combinations of inclusions in quartz crystals
from Almadén, Spain - a famous and historic mercury deposit renowned for its cinnabar specimens.

AERINITE - Spray of acicular crystals included in quartz.

Cinnabar - a distorted crystal included in quartz.

Native mercury - silvery bleb inclusions in quartz.

Zoned cinnabar and native mercury in quartz.

Unzoned inclusions of cinnabar and native mercury in quartz.

Mineral Inclusions - Not Just in Quartz

Mineral inclusions and impurities are not restricted
to quartz alone. It is a habit which prevails
throughout the Mineral Kingdom.

One such recent example is that of heulandite from the Deccan Plateau of India. It has been found in this region
as fine, crystallized examples in several colours:
green (chlorite-filled), red and mustard-yellow.

Another example is the black calcite specimens from Herja, Romania - the colouring caused by inclusions of the antimony species jamesonite/ boulangerite.

Indeed, the type locality specimens of heulandite,
that occur in the Clyde Plateau Lavas of central Scotland,
are typically red in colour. (see Glasgow area).

HEULANDITE - Maharashtra, INDIA.
A crystal group coloured by mineral inclusions.