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About Us


The most important element in jewellery is its design, and the gemstone is the centrepiece of that design.

What we do

At Caldera Gem we specialise in exquisitely cut coloured gemstones, ideal for engagement rings, bespoke jewellery and custom designed jewellery. Our customers can source a unique and natural gemstone online from our store and take it to their local artisan  jeweller to be transformed into a truly original piece, unlike no other.

Our curated selection is meticulously hand-picked, showcasing one-off diamonds, sapphires, rubies, aquamarines and other precious gemstones.

Why choose us?

Roots run deep and our history in the gemstone business goes back generations. Knowledge handed down has provided us with deep expertise, long established relationships with trusted cutters, miners and traders, and an expert eye for quality.

We are trained and qualified gemmologists. Experts in gem cutting, sourcing and quality. We take the risk and the complexity out of sourcing exceptional gemstones, focusing on quality, cut and make. We are extremely passionate about our products, offering a refined range and only supplying the best.  

When you choose from our exclusive selection, you can relax, knowing we have mastered the art and science of sourcing quality gemstones that really make a statement and will maintain their value for many generations to come.

Who are we?

Created by Joy Thavat, Caldera Gem continues a long legacy and successful history of gemstones in her family. With a focus on Australia, the USA, Europe and the UK, we provide the highest quality sapphires and precious gemstones at the best prices with fully insured shipping.

In 1911 Joy’s paternal great-grandfather, Ming Hui, left China for Thailand. In Bangkok, he learned the artisan craft of gemstone cutting. Over the years his passion and brilliance became well known and he was widely respected for his ability to draw out the beauty in the gemstones that he cut.

His eldest son, Joy’s grandfather, Wichai, married her grandmother Lakshmi in 1948. They ran a successful store in Bangkok’s Chinatown, trading jewellery, gemstones, porcelain and antiques. In 1973, with their son Thawat (Joy’s father Paul) they opened Lakshmi Gems on the corner of Mahesak & Silom Roads. This area was and remains the gemstone trading centre of Bangkok and the world.

Joy’s father Paul travelled to New Zealand in 1970 and it was here he met her mother. By 1974 they were married in Bangkok and in 1976 they returned to New Zealand where he established his diamond and gemstone wholesale business, Precious Gems. For over 30 years he would make frequent trips to Bangkok, Sri Lanka, India, Hong Kong and sometimes further afield, to source rare gemstones and diamonds for the market here.

“I grew up with gemstones in my life. My father had all manner of tools and machines, not to mention gemstones, to fascinate a small child. For as long as I remember there was always jewellers loupes and gem tweezers in our home. As a teenager I would travel to Bangkok annually and wander around Silom Rd admiring all the artisan crafts, including gemstones, that Thailand is so famous for.”



After university Joy lived in Sydney for over a decade, studying commerce and working in business management. In 2016 she chose to return home to study gemmology and continue the family business and legacy.

“After extensive travel sourcing gemstones, I started to realise that our standard for quality was a lot higher than many others. I could cover blocks of Bangkok and giant halls of an international gemstone fair and know that the gemstones we source really are world class quality. Back home I realised that many jewellers felt frustration at the lack of awareness and appreciation in the market for quality hand-made jewellery.”


In 2019 Joy launched Caldera Gem. The idea was to create an online space to share her family’s knowledge, give people access to their exquisite gemstones and promote the incredible skill and talent of artisan jewellers and goldsmiths.

Both Paul & Joy hold the prestigious and globally recognised Gemmology Diploma from Gem-A (Gemmological Association of Great Britain).

In addition, they are both qualified, advanced diamond graders with GIA (Gemological Institute of America) and GAA (Gemmological Association of Australia).


Why choose custom made jewellery?

Buying jewellery is an investment. It therefore makes sense to invest in a quality, individualised piece that reflects your character, your story and your personal taste.

There is simply no comparison in quality and form when comparing mass-produced jewellery with the workmanship of hand-made jewellery that has been crafted by a master goldsmith jeweller. These skilled craftspeople can bridge the gap between design and wear and will bring your unique and original idea to life.

Jewellery denotes more than simple status and wealth. It is a creative expression of who you are. You were born an original, not a copy. A truly unique piece of jewellery honours this. Likewise, giving jewellery to someone you love is more meaningful and symbolic when time, thought, and creativity has gone into its design.