[syhprum (OP)]

The market for diamond jewellery is a very manged one, can man made diamonds equal natural ones

[chiralSPO]

Man can certainly manufacture small diamonds (up to a few carats, I believe) that are as perfect (or more) than what can be found in the ground, either using a high pressure synthesis, or chemical vapor deposition. I don't know if we are capable of growing enormous diamonds like those that form in the Earth's mantle (the largest diamonds unearthed so far are a few thousand carats¹, but there is also evidence of multi-ton diamond lurking in the mantle²), but a quick google search sent me to a page that claims that we have made diamonds over 100 carats³:

There are also manufactured alternatives to diamond, if you are considering use for jewelry:
Silicon carbide (Moissanite), pure alumina (colorless sapphire), and cubic zirconia are all reasonable diamond substitutes, depending what you want.

1) https://www.history.com/this-day-in-history/worlds-largest-diamond-found
2) https://www.nationalgeographic.com/science/article/news-earth-diamonds-gems-rare-minerals-earthquakes
3) https://www.1215diamonds.com/blog/how-big-lab-grown-diamonds-get/

[Petrochemicals]

Last time I read, Synthetic diamonds of gem quality where still difficult to produce due to the flaw inclusions and other impurities, vapour deposition being the most reliable form due to . It was  possible to make gem quality diamonds economically up to about a quarter of a carrot. Diamond production using different techniques are getting better and more economical, production yields many useful monocrystaline diamonds for industry. Polycrystalline diamonds are also made but they crumble and are only many small diamonds, stuck together.

I was reading into the possibility of manufacturing coloured diamonds, far more expensive than white, thus the economic argument goes out the window. The process of vapour deposition with the required impurities for colour is possible but as of yet it is impossible to produce large diamonds in colour in the sufficient quality to make it viable.

[Bored chemist]

a quarter of a carrot.

LOL

[Colin2B]

.......up to about a quarter of a carrot.

I really do think that isn’t going to help your 5 a day

[evan_au]

There are many applications of diamonds as abrasives (eg angle-grinder), cutting tools (eg drilling for minerals), laser windows and high-voltage/high-temperature semiconductors. These latter two applications cannot be met with natural diamonds.

The poor labour practices (eg child labour and minimal safety measures), suspect sources (eg warlords) and pyramid-scheme pricing for natural diamonds means that some people may prefer artificial diamonds on ethical grounds.
https://en.wikipedia.org/wiki/Synthetic_diamond

The traditional diamond traders would want to distinguish the "artificial/manufactured" diamonds from their "superior/natural/symbol of love" jewelry product (and denigrate the former).
- Just like natural pearls were distinguished from the artificial/seeded/cultured pearls in jewelry
- Today most of the pearl market is with cultured pearls, and people accept this
- And even enjoy the graded sizes and fancy shapes you can easily assemble with seeded pearls
- Also helped by the much lower cost, and environmentally-friendly aspects (I understand that natural pearls occur in about 1 oyster out of 10,000, while you can grow several seeded pearls in each oyster)
- I expect that in time, just like pearls, most of the diamond jewelry market will eventually accept (and even prefer) manufactured diamonds
- That's find with me - as long as people know what they are buying, they should be free to choose.

manufacturing coloured diamonds, far more expensive than white

One technique is to take a white diamond, and put it in a particle accelerator.
- Electrons fired into the crystal lattice become trapped, giving the diamond colour, and greatly increasing its value
- Naturally, the industry developed techniques to identify these "faked" coloured diamonds

[Petrochemicals]

One technique is to take a white diamond, and put it in a particle accelerator.
- Electrons fired into the crystal lattice become trapped, giving the diamond colour, and greatly increasing its value
- Naturally, the industry developed techniques to identify these "faked" coloured diamonds

Does this result in the same colour or can it be varied?

.......up to about a quarter of a carrot.

I really do think that isn’t going to help your 5 a day

Bah, I realise my folly too late.

[evan_au]

Does this result in the same colour or can it be varied?

There are a number of techniques to change the colour of a natural diamond to various hues (or to improve its clarity, also quality-enhancing).

Irradiated diamonds are all some shade of green, black, or blue after treatment, but most are annealed to further modify their color into bright shades of yellow, orange, brown, or pink.

See: https://en.wikipedia.org/wiki/Diamond_enhancement#Color_enhancements

[Iannguyen]

A diamond that has been grown in a controlled laboratory environment is known as a lab-grown diamond. Scientists may now produce diamonds that visually appear like earth-mined diamonds and have the same chemical and physical properties using the common technologies of Chemical Vapor Deposition (CVD) or High-Pressure High Temperature (HPHT).
Natural diamonds and lab-grown diamonds look identical and have the same hardness and durability. The distinctions between natural and lab-grown diamonds are not visible to the human eye. Natural diamonds contain trace levels of nitrogen, but lab-grown diamonds don't. This is one of the indicators gemologists use to determine whether a diamond is synthetic or natural. Natural diamonds are formed over millions of years by the pressure of the earth's crust, then mined, cut, and polished. A Lab-Grown Diamond is subjected to the same conditions as a natural diamond but in a laboratory setting. In reality, the procedure for creating a Lab Grown Diamond reduces the time it takes to produce a diamond from millions of years to a few months. The Lab Diamond is then cut and polished as well. Man-made, synthetic, cultivated, or artisan diamonds are all terms used to describe lab-grown diamonds. A consumer may become perplexed due to the interchangeable wording. However, each phrase refers to the same thing: a certified diamond that has been 'grown' in a laboratory. Lab-Grown Diamonds are sometimes referred to as CVD or HPHT, which simply refers to the diamond-making method.