Displaying our Earth science specimens

by Robin Hansen, Curator, Minerals and Gemstones, NHM Earth Sciences

​​As part of the Galley Enhancements​​ Programme to refresh the Museum’s Earth Galleries Ground Floor, we’ve been working on the specimens to improve the experience for visitors, improve collection visibility and update the science.

This project brought together a team of experts from across the Museum:

  • Beca Jones, Project Management
  • Amy Wedderburn, Interpretation
  • Claire Kelly, Conservation
  • Mike Peel, Mount Making
  • Joe Rodrigues, Engineering
  • Sameh Sharif, Special Effects
  • Katherine Horton, Design
  • Robin Hansen, Science
  • Noemi Moran, ES Loans Officer
  • and coordination with Security and Retail.

We had to work over the past six months by stealth, although a few eagle-eyed colleagues will have noticed us working in the portholes in the mornings on their way in. We successfully:

  • replaced missing specimens
  • updated science content. Curators, the scientific experts on these objects, worked with Interpretation to produce accurate and informative text.
  • improved lighting, installing lights above labels and custom adjustments to highlight each specimen
  • cleaned , reported on condition, and photographed specimens, either in situ or by temporary removal

It is incredible how these small tweaks have made a vast improvement.  Nine new specimens have been added, with custom mounts created to hold challengingly shaped or heavy specimens.  Highlights of the new specimens are:

​Gypsum

Fishtail Gypsum Earth Gallery Porthole specimen 2019

​​This magnificent specimen from Romania features a ‘fish tail’ V-shaped twinned crystal which stands proud from the yellow host mineral Dolomite. Gypsum is the most common sulphate ​mineral, is very soft, and normally forms as veins of massive (non-crystalline) material. It is used for making plaster, and even carved to make sculptures in a form known as alabaster. Translucent well-formed crystals such as on this specimen are known as selenite.​

​Glowing minerals

New lighting has been installed above the two fluorescent minerals fluorite and willemite. Previously these specimens were shown only under ultraviolet light, exhibiting the property of fluorescence. Fluorescence is a phenomenon which occurs when a mineral is energised by a type of energy, in this case ultraviolet light. As the mineral reverts to its previous energy state it releases energy of a lower level, in this case light within the visible spectrum (i.e. that our eyes can see) and appears to glow. The new lighting shows the specimens under normal lighting conditions (left image above) and UV lighting (right image above) so that the fluorescent effect is clearly seen by the colour change.​

​Gold

Gold Earth Gallery Porthole specimen 2019

This small but rich specimen (on the right of the picture) is formed of dense gold wires intergrown on white quartz crystals. It comes from the USA. It accompanies a silver specimen from Norway which also shows wire crystals growing from white calcite. When gold and silver – metallic elements – form pure crystals without combination with any other elements they are known as ‘native’. In fact, gold prefers to grow pure which is why it is commonly found as gold nuggets and not combined into other minerals. Crystallised gold, that is gold that has formed in crystals, is rare in nature and wire formations are even rarer.​

​Pyrite

Pyrite Earth Gallery Porthole specimen 2019

A new pyrite specimen was acquired to replace another which sadly was suffering from pyrite rot. This new large specimen comes from Peru and consists entirely of intergrown cubic crystals of pyrite. It has very bright metallic lustre which is almost mirror-like – this is entirely natural and typical of pyrite; it has not been polished.​

​Vanadinite

Vanadinite Earth Gallery Porthole specimen 2019

The small red sparkling crystals catch the eye on this large specimen. They contain the element vanadium which is used in metal alloys to improve their strength and resistance to heat. This specimen comes from Morocco, which is famous for producing these red vanadinite crystal specimens.​​​

​​Amethyst Geode

Amethyst Geode Earth Gallery Porthole specimen 2019

A new larger and deeper coloured amethyst geode has been acquired specifically to display in the portholes. This new specimen is taller with darker purple crystals providing a more eye-catching display. Geodes occur in rounded cavities from gas bubbles trapped in cooling molten rock (i.e. lava), and the rock solidifies around the bubble. The gas seeps away, and silica rich fluids flow through these cavities, crystallising on the margins as amethyst, growing in towards the centre in sparkling pyramidal crystals.​

​Fossil amphibian skull (Diplocaulus magnicornis)

Fossil amphibian skul Earth Gallery Porthole specimen 2019

Angela Milner and Sandra Chapman write: This skull belonged to an aquatic animal that lived about 295 million years ago. The flat boomerang shape is unique in the animal kingdom and it is not related to any animals living today. It rested at the bottom of rivers and streams. The expanded corners of the skull may have functioned as a hydrofoil, providing lift against water currents as it tilted its head to rise to the surface to snap up small prey. This unusual skull is both weird and functional!​

​Rhodochrosite

Rhodochrosite Earth Gallery Porthole specimen 2019

This sweet specimen features a single pink rhombohedral rhodochrosite crystal on white spiky quartz crystals. Rhodochrosite is a manganese carbonate. It hails from the Sweet Home Mine in Colorado which is famous for producing incredible rhodochrosite specimens, and in fact this specimen was donated by the company which mined it. It sits in front of a large polished slab of rhodonite, a similar mineral of manganese silicate. Both are coloured pink by the manganese.​

​​Brittle stars (Palaeocoma milleri), Sea lilies (Balanocrinus gracilis)

Brittle Stars Earth Gallery Porthole specimen 2019

Tim Ewin writes: Finding articulated fossil crinoids and brittle stars is rare, as their multi-plate skeletons are held together by soft tissue which decays rapidly on death (often within three to six days). They are only preserved in rapid, deep and permanent burial (brittle stars can dig through up to 5 cm of sediment to escape). The fact these specimens have been preserved and also retained their three-dimensionality is highly unusual. From burial experiments we’ve learned brittle stars adopt various spiralling positions with their arms to dig out of sediment; trying to cork-screw the disk out, even shedding trapped arms to escape. These postures, including using the crinoid stems for extra purchase, are evident in this specimen. It has a dynamic appearance, capturing a moment in time some 180 million years ago, when the group were overwhelmed by sediment during a storm. The site these fossils came from has been known for over 200 years (indeed Mary Anning sold brittle stars from the same locality – some of which are in the NHM collection!), it is only with the advent of modern preparation techniques using air abrasives and air pens, that their full beauty and dynamic nature of preservation has been realised.​

​All images © The Trustees of the Natural History Museum

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