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Phosphosiderite Properties Facts and Photos

phosphosiderite mineral sphere

What is Phosphosiderite?

Phosphosiderite is a relatively rare mineral first discovered in 1858.  It was named in 1890 after its main constituents which are phosphate and iron.

The name phosphosiderite comes from 'phospho' (from phosphate) and 'siderite' from the Latin 'sídēros' meaning 'iron'.

This naturally occurring form of iron phosphate can only be found in a handful of locations worldwide.  Most material comes from Germany, USA, Portugal, Chile and Argentina.

Although once known as metastrengite this name is now mostly obsolete.

Crystals occur in shades of red and pink and tend to be extremely small.  Phosphosiderite occurs more widely with a massive or botryoidal crystal habit.  This material is mainly used for lapidary purposes.

In mineralogy crystal habit describes the external shape of a crystal or group of crystals and how well it/they have formed.  The habit described as massive means the mineral has masses of crystals with no visible internal structure and no distinguishable external shape.

An good example of a mineral whose crystals occur in this way is turquoise. Crystal habit described as botryoidal means the crystals have a rounded shape.  The word comes from the ancient Greek word 'botrys' meaning 'bunch of grapes'.

the mineral turquoise embedded in rock matrix

 Turquoise mineral embedded in rock matrix

malachite with a botryoidal crystal habit

 Malachite with botryoidal crystal habit

The phosphosiderite that occurs in massive form can be found in striking shades of lilac, lavender and purple.  Most of this material is transformed into cabochon gemstones.

This stone can feature yellow spidery veins which are inclusions of cacoxenite (pronounced ka~cox~enite).  This iron aluminium phosphate mineral usually but not always occurs within other minerals

On Mohs scale of mineral hardness phosphosiderite grades 3.5 to 4 which means it's quite soft.  It's also brittle so must be handled carefully.

Article Photos

The photos of the minerals turquoise and malachite are clickable and redirect to the original non-compressed image.  Photos courtesy of Stan Celestian (turquoise) and Ron Wolf (malachite).  

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