Where am I in the gemstone pipeline?

A polarised filter showing distinct colours of a thin long green crystal on a bright light

This is a reproduction of a reflective piece of writing I completed for my Gem-A Foundation in Gemmology in February 2022. Image above: Examining the strong dichroic (two-colour) pleochroism of a green tourmaline crystal using Gem-A’s London dichroscope with a flatlight (credit: Tehmina Goskar).

What is the gemstone pipeline?

The gemstone pipeline considers all of the stages, processes and people involved in the world of gem materials, from mine to market. It should include knowledge of geology, mining and sorting, lapidary work (gem cutting), lab creation of synthetics, metalwork (e.g. gold and silver smithing), jewellery design, loose stone dealing and retail, as well as research, appraising and valuing, reuse and remodelling. Here are some of the ways my previous work has helped me understand a gemstone’s journey. I have also begun to think more widely about gem materials which can be any material used to make objects for adornment, ornament and display and do not just have to concern gemstones and precious metals. These might include cheap materials like plastics and organic materials like paper, paint and plant fibres.

Mining history

I live in a geologically diverse and rich part of Cornwall, UK, mainly known for its high-quality metalliferrous deposits found in granite, particularly copper and tin. The last economically-viable mine, South Crofty, closed in 1998. Since the Bronze Age, Cornwall has produced alluvial gold, silver, later in the industrial period (from the 18th century) a whole host of other metals and materials have been mined here including titanium, tungsten, arsenic, manganese, and so much more.

In 2006 several areas in Cornwall and West Devon were designated as the Cornish Mining World Heritage Site for its hard-rock mining history. It was through the documentation and interpretation of this industrial heritage that I first learned about mining and what it involved historically, compared to today. I have curated several exhibitions that have included the topics of mining and the metal supply chain, particularly that of copper (both here in Cornwall and in Wales where I used to live). Today, the most sought-after Cornish mineral that is economically viable is lithium and also rare earths such as indium, for use in batteries and electronics, and there are several prospecting companies here venturing once more. 

Tin (cassiterite) assay samples on display at Geevor Tin Mine, Pendeen, Cornwall, UK (credit: Tehmina Goskar).

I have a good friend who is an ex-miner from South Crofty from whom I have learned a lot. He started training as an assayer (to determine the metal yield of different parcels of ore) then he moved to the underground. This was in the late 1970s, early 1980s. He often tells us that he was always shocked at how old-fashioned the methods of extraction still were, using essentially 19th-century techniques such as tramways, persisting with using ‘black powder’ to set up ’rounds’ to explode the metal-bearing rock. He said his mine captain didn’t like “modern” dynamite.

Rounds were regularly spaced out holes drilled with rock drills (usually pneumatic and these were substantially designed in Cornwall and shipped all over the world, including for diamond mining up until the 1960s and 1970s) to form the round in the rock face. Spacers were used where there were soft parts detected in the granite and then it was exploded. Very unhealthy for the miners, many of whom had short lives or long-term health problems like silicosis. My friend left tin mining early because his doctors warned him against too many years underground. He also recalled some horrifying events where misfires ended up with gallery collapses and the death of co-workers.  

Fossicking and collecting

I’ve posted a few times about my fossicking on the beach for interesting pebbles. Living in a geologically-diverse region means I can see much of the geology we have learned about in action (e.g. on Friday I went to The Lizard which is formed largely from serpentine – essentially an area of the oceanic crust/earth’s mantle that has protruded up over the top of the continental crust). My local beaches are dominated by quartz and I have found several interesting, though mainly polycrystalline quartz specimens, especially agates.

A chunk of greenish, yellowish rock resembling snake or lizard skin on a dark slate hearth.
A large chunk of green serpentine rock I recovered from a beach near me following the huge Valentine’s Day storm in 2014 where a large part of our beach and promenade was damaged. It is right across the bay from The Lizard. Serpentine comes from ‘ophiolites’, places where rock formed near the Earth’s mantle and bottom of the oceanic crust obduct over the top of nearby continental crust. I thought it was pretty cool to have a piece of the earth’s mantle on my fireplace!

I also have a small but diverse mineral specimen and crystal collection and studying on this course has breathed new life into my understanding of them. In addition to my beach finds, I have some interesting specimens from old mine dumps, particularly clusters of quartz and calcite. I also have a couple of interesting specimens of other Cornish minerals relevant to gems, a piece of  turquoise (these come from the china clay or kaolin areas of mid-Cornwall which are being worked to this day by French company Imerys) and opal (common, not precious). This is usually not gem-quality but in the museum where I currently work, there is a ring someone made with some Cornish turquoise. I have also worked with some museum mineral collections in the UK, where I have come across some extraordinary historical specimens from mines that are now long-flooded and inaccessible.

Studying historical jewellery

My PhD looked at early medieval metalwork, including jewellery, amongst other forms of moveable wealth, particularly that belonging to and being inherited by women. Through this work I got familiar with how jewellery and their gems, and other high value items, were valued for the security it gave families, evidenced through wills and marriage contracts as well as fines. I was fortunate enough to undertake research on jewellery collections at the British Museum and V&A as well as several in Italy and the USA. These pieces had historically or more recently been recovered from archaeological excavation, and later deposited at museums. Unfortunately documentation about the exact places and contexts where many of these pieces came from was generally poor.

Most of the gem materials I encountered in these mainly gold objects were pyrope-almandine garnet, red enamel simulating garnet, coloured glass paste, amethysts and carnelians, seed pearls, as well as the reuse of older coins, carved gems or intaglios from the Roman period (usually agate or onyx). Apart from cloisonné (cold-cut inlay) all the gemstones I came into contact with were cabochons or rudimentary beads. My period of study covered the 8th to 12th centuries, after which is when the European fascination with, and access to, coloured gemstones really took off, particularly the West. 

early medieval large elliptical gold ring set with a Roman agate intaglio and cloisonné garnets
Early medieval gold ring from southern Italy with garnet cloisonné inlay and a reused Roman-era onyx intaglio in the collection of the Museo Archeologico Nazionale di Napoli, Italy (credit: Tehmina Goskar).

Jewellery collection

I have a small jewellery collection with coloured gemstones and pearls. Some of these pieces have come down to me has family heirlooms. Since starting this course I’ve been chatting with my mum about my own family connections with gems and jewels. Apparently some of our ‘great-great’ generation were diamond polishers (hand cutting) in India and one of my great-great grandparents was a diamond merchant but as yet I have not been able to find out anymore.

I think it is fair to say I am quite addicted to and eternally fascinated by jewellery and have attempted to verify the identity of different gemstones in them as part of practising the skills we have learned, for example, a silver necklace I had been told was set with all different coloured topazes from Sri Lanka. I have figured, thanks to my new skills with the polariscope and spectroscope, that they are no such thing! Mind you, I was quite pleased to identify them as alternating zircons and garnets. I also love honing my skills with the different gemmological instruments.

Zircons and garnets from Sri Lanka set in a silver necklace shown with transmitted light. From left to right are alternating green zircon, purple pyrope-almandine garnet, yellowish-green zircon, red pyrope-almandine garnet, green zircon, purple garnet and a central pinkish-brown zircon (credit: Tehmina Goskar).

Similarly I have been able to identify a synthetic ruby likely dating to the late 1920s, in a ring belonging to my grandmother. My family did go through the process of appraisal with some of the pieces so it was interesting to see that in action by a trained gemstone appraiser and valuer. I have learned a lot from her.

What do I want to do next?

I like pieces with a story or a history to them and would love to develop a career based on appraisal, research, and bringing different cultural interests in gemstones, history and storytelling to designers, investors and purchasers. As a curator I also have responsibility for monitoring the physical environment of objects so I am very experienced in understanding the effects of light, UV, temperature and humidity change on different materials. Understanding gemstone durability and stability is absolutely essential in successful jewellery design.

A favourite objects at my museum, a Cornish turquoise cabochon and silver ring donated to the Museum of Cornish Life, Helston, UK by Kid Wood (credit: Tehmina Goskar).

Museums curators have traditionally been quite separate from valuers and auctioneers but there is much in common, and one helps enhance the reputation of the other, I think, particularly when it comes to gemstones and jewellery. I am also interested in the major ethical issues surrounding the gem trade, not just to do with the environment but also the provenance of items, avoiding dealing in looted items, weighing up the social and economic benefits of mining and extracting natural gem stones vs. synthetic stones. Museum ethics is an area I have a lot of experience in, including practical considerations such as collecting and lending items controlled by CITES (Standing Committee of the Convention on International Trade in Endangered Species) and would love to try transferring my skills in a job in the commercial art world/gem world one day.

I also like the idea of professionally writing about gems and jewellery. I enjoy reading some of the blogs and posts by gem and jewellery ‘influencers’ online and think they are an important part of enhancing the integrity and visibility of the gemstone and jewellery trade to the general public. I would also consider looking after a private or research gemstone and jewellery collection. One of the problems with curating gem and jewellery collections in public museums is that they are artificially separated into geology or earth sciences (rough minerals and loose gems) and design or decorative art (finished jewellery objects) which when we consider the gemstone pipeline seems a bit of a shame. Update 21 March 2024: I am currently developing an academic research project on university gem and jewellery collections which will challenge this disciplinary divide.