Unlocking the Mysterious Mineral Box

 

Museum Minerals

 

I recently met with Robin Hansen, a curator at the Natural History Museum in the Minerals division for a sneak peek of some of the minerals going into a new exhibition.

 

Robin is an award winning gemmologist, previously working with private collectors. I really valued Robin's expertise to unlock some of the secrets behind how these amazing specimens form. 

One in particular really fascinated me, it was large and matt with cube shaped hollows all over the surface this was an Epimorph.

 

 
Quartz Epimorph Image from Crystal Classics: "specimen shows cubic edged impressions of pre-existing probable Fluorite crystals measuring to 3.5 on edge"

Quartz Epimorph

Image from Crystal Classics: "specimen shows cubic edged impressions of pre-existing probable Fluorite crystals measuring to 3.5 on edge"

Example of cube shaped Fluorite Image reproduced from the 'Mineral Images Gallery' of the Mineralogical Society of Great Britain & Ireland (www.minersoc.org")

Example of cube shaped Fluorite

Image reproduced from the 'Mineral Images Gallery' of the Mineralogical Society of Great Britain & Ireland (www.minersoc.org")

 

 

Epimorph:

A HOLLOW CAST LEFT BY A MINERAL THAT HAD GROWN OVER AN INITIAL MINERAL WHICH HAS DISSOLVED AWAY.

 

 

 

 

There would have originally been a specimen of fluorite, formed from crisp angular cubes which this other mineral had grown around.

 

There is a beautiful and intriguing example of an Epimorph currently on display in “The Vault” at the Natural History Museum.

 

The mystery of this particular example is that the original inner mineral should have dissolved before the outer box, so we're not sure exactly what caused this epimorph to form.

 

What is particularly beautiful is how another mineral has started to grow inside the cavity left behind.

 
Box epimorph of siderite after fluorite from the Virtuous Lady mine in Devon. Image courtesy of Jolyon & Katya Ralph from www.Mindat.org

Box epimorph of siderite after fluorite from the Virtuous Lady mine in Devon. Image courtesy of Jolyon & Katya Ralph from www.Mindat.org

So now, to investigate this amazing process further and how it links to jewellery see my next post coming up where I visited Glyndwr University’s jewellery and metalwork department the same week for a demo on Investment Casting.