Ethical Sourcing | Crafted by Hand | Lifetime Warranty

Our Centre Stones

Discover the Range.


Each LMK diamond is hand-picked in house by Lydia and selected for its superlative radiance and exceptional fire and brilliance.

All of our diamonds reach a clarity grade of SI or above, and are colourless, bright stones, ranging D - H.

We do not set any of our pieces with 'commercial grade' diamonds - the difference in sparkle between our diamonds and those commonly available is obvious when you see them in person.

If you wish to select your own diamond in person, you are welcome to visit us in London.

Request a diamond-viewing appointment 


Please Note: Carat weights listed for each ring are approximate weights.

Each diamond is unique, and we select the stone which best reflects light whilst fitting perfectly into your chosen designer ring.

EXAMPLE: Should you order a one carat centre stone, your actual diamond weight will be 0.95 - 1.10 carats.

Committed to Luxury, Ethics, and You

We are committed to making sustainable luxury affordable to anyone who appreciates refined craftsmanship, regardless of budget.

As part of that endeavour, we include a complimentary moissanite centre stone with every design - perfect for those whose budget does not stretch to a diamond.

Read on to discover more about our ethical natural diamonds, lab-grown diamonds, moissanite, and other precious gemstones.

Natural Certified Diamonds

Our natural diamonds are ethically sourced from trusted partners. Each partner is regularly vetted, and must meet the LMK Green Rating™ in addition to internationally recognised ethical standards.

Each stone comes with a GIA or LMK Certificate and is guaranteed conflict-free.

Click here to discover Ethical Diamond Engagement Rings

Luxury Lab-Grown Diamonds

Lab-grown diamonds are real diamonds. All diamonds are made of crystalised carbon, and can be created deep in the earth, or above ground using technology.

Each Lydia McCarthy-Keen Lab Grown Diamond must meet rigorous standards as part of the LMK Green Rating™ assessment.

We require all partners to be actively utilising and increasing their use of renewable energy in the process of crystalising carbon into an LMK Lab Grown Diamond.

Next, the stone must excel in scintillation, fire, and brilliance, and be comparable to the beauty of our natural diamond counterparts.

Every Lydia McCarthy-Keen London Lab Grown Diamond comes with an IGI or LMK Certificate.

Click here to discover Lab Grown Diamond Engagement Rings

LMK Moissanite

Moissanite is a top-of-the-range diamond alternative, made from silicon carbide.

It was first discovered in asteroids, yet there isn't enough on earth for jewellery-making, so we grow it in a lab.

It's very sparkly and unlike cubic zirconium is very durable, making it a great long-term choice. It is also a budget-friendly option for those who might wish to upgrade to a diamond later.

We include a complimentary LMK Moissanite centre stone in all of our ready-to-wear engagement rings as part of our mission to make luxury engagement rings affordable for everyone.

Each stone is accompanied by an LMK Certificate of authenticity.

Click here to Discover Moissanite Engagement Rings

Coloured Diamonds, Sapphires, Rubies, and Emeralds

In addition to ethical and lab grown diamonds, we can offer all the major precious and semi-precious gemstones upon request.

For those who fantasise about nature's most vibrant and characterful hues, an LMK Coloured Diamond or Gemstone envelopes the wearer in one of nature's rarest and most elaborate works of art.

We specialise in both natural and lab grown yellow, pink, and chocolate diamonds, as well as colourful gemstones.

For sourcing requests, please click here to Get in Touch.

The LMK Difference

All of our diamonds reach a VS or VVS clarity grade with a D-G colour and Excellent cut grade as standard.

Our natural diamonds and gemstones are ethically sourced from trusted partners. Each partner is regularly vetted, and must meet the LMK Green Rating™ in addition to internationally recognised ethical standards.

We apply the same ethical rigour to our lab grown diamonds and expect our partners to be actively utilising and systematically increasing their use of renewable energies year-on-year.

Once a prospective LMK Diamond™ has passed ethical assessments, we cut only those which display the optical properties associated with perfectly aligned angles and facets.

We reject over 98 percent of diamonds and only those which Lydia has selected as worthy for her to wear herself are destined to become an LMK Diamond.™