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The vibrant, passionate colour of rubies makes them one of the most distinguishable gemstones – and one of the most desired!
Red is often associated with passion and romance, so ruby jewellery is often gifted to loved ones, while vintage ruby engagement rings are a consistently popular choice. or featured in engagement rings. They are also associated with 40th wedding anniversaries as well as being the birthstone for the astrological sign of Cancer and the birthstone of July. There are plenty of excuses to invest in ruby jewellery!
If you’re interested in adding some of these bold gemstones to your collection, we’ve put together a beginner’s guide to rubies that can help you. Read on for an introduction to the basics of rubies and a few guidelines as to what to look out for when buying.
How are rubies formed?
Ruby is the red version of the corundum mineral group – all other colour variations are classed as sapphire. A ruby is formed when traces of chromic oxide is present with a corundum crystal, giving the ruby its distinctive hue. The red colour’s strength depends on how much chromium is present; as little as 1% of the overall chemistry can produce a deep red.
The colour of a ruby can range from a pinkish red – as seen in this Edwardian 3.17-carat ruby and rose ring – to a much deeper, more mysterious red, such as in this 65.00-carat natural unheated cabochon ruby pendant. Rubies with a deeper, richer colour tend to be more valuable.
Mohs Hardness Scale
Rubies score 9 on the Mohs Hardness Scale – making them one of the hardest gemstones on earth.
| Hardness | Substance or mineral |
| 0.2–0.3 | caesium, rubidium |
| 0.5–0.6 | lithium, sodium, potassium, candle wax |
| 1 | talc |
| 1.5 | tin, lead, graphite, ice |
| 2 | calcium, cadmium, sulphur, bismuth |
| 2–2.5 | rock salt, fingernail, mica |
| 2.5–3 | gold, silver, aluminium, zinc, jet |
| 3 | calcite, copper, arsenic, chalk |
| 3.5 | platinum |
| 4 | fluorite, iron, nickel |
| 4–4.5 | ordinary steel |
| 5 | tooth enamel, zirconium, palladium, obsidian (volcanic glass) |
| 5.5 | beryllium, cobalt |
| 6 | titanium, manganese, germanium, uranium |
| 6–7 | opal, peridot, tanzanite, jade, garnet |
| 7 | quartz, rhenium, vanadium |
| 7.5–8 | emerald, beryl, zircon, spinel |
| 8 | topaz, cubic zirconia, hardened steel |
| 8.5 | chromium, silicon nitride, tantalum carbide |
| 9 | corundum (includes sapphire and ruby), titanium nitride, aluminium oxide |
| 9–9.5 | silicon carbide (carborundum), titanium carbide, aluminium boride, boron carbide |
| 9.5–near 10 | boron, moissanite (crystal form of silicon carbide) |
| 10 | diamond, carbonado |
What other features do rubies have?
Most other varieties of corundum are internally clean and clear, whereas rubies can be expected to have inclusions (internal imperfections).
Depending on whether these are large or small inclusions (often called 'silk'), the cost and durability of the ruby will be affected. The 'cleaner' the stone, the more valuable it will be.
As it is incredibly rare to get an inclusion-free ruby, if you have a perfectly clear one, it is a good idea to test it, as it may be synthetic.
If you have any questions regarding this precious jewel, get in touch with us today, and we'll be sure to help in any way we can.