Gemstone Materials & Lab-Grown Processes: A Complete Guide

ZGEMS KNOWLEDGE CENTRE · GEM MATERIALS & MANUFACTURING

What makes a ruby a ruby? Is a CVD diamond “real”? Why can two lab-grown sapphires have very different prices? This guide explains the material behind common gemstones, how natural gems form, and what happens inside laboratory growth systems.

Includes mineral identities, seven growth/engineering methods, gem-by-gem comparisons and realistic cost-versus-quality guidance. Updated November 2026.

Natural, lab-grown, treated and simulated: four different things

Natural gemstone

A gemstone material formed through geological or other natural processes and later mined or collected. Natural stones can also be treated.

Lab-grown / synthetic

A manufactured counterpart with essentially the same mineral identity, chemistry and crystal structure as the named natural material.

Simulant

A lookalike with a different material identity, such as cubic zirconia or moissanite used to resemble diamond. It is not lab-grown diamond.

Treated gemstone

A natural or lab-grown gem whose colour, clarity or appearance has been altered after formation, for example through heat or other methods.

Composite / assembled

A product made from more than one piece or layer, or containing stabilisers or other materials. It should be described by its actual construction.

Colour-style name

Terms such as “Paraiba-colour” describe an appearance. Colour alone cannot prove a mineral species, growth process, mine or country of origin.

The key rule: natural versus laboratory-grown describes origin; ruby versus spinel describes material; flame fusion versus flux describes manufacturing method; and a colour grade describes appearance. These are separate questions.

How natural gemstones form

Natural diamond crystallises under conditions involving high pressure and temperature deep within Earth. Ruby and sapphire are corundum formed in suitable metamorphic or igneous environments. Emerald-bearing beryl may crystallise in fluid-rich geological systems, while quartz often fills cavities through mineral-bearing fluids. Natural gem formation is affected by geology, trace elements, growth interruptions and inclusions. A laboratory uses controlled conditions to grow an equivalent crystal where technically possible; it does not copy the entire geological history.

Common gemstone minerals and what they are made of

Two gemstones may share a colour while having different chemistry, hardness and care needs. Conversely, ruby and sapphire share the corundum mineral structure despite appearing in different colours.

Mohs values are approximate scratch-hardness guides, not measures of toughness or fracture resistance.
Gemstones Actual material Mohs hardness Natural vs lab-grown Important distinction
Diamond Carbon, C 10 Natural diamond formed under geological conditions; HPHT and CVD grow diamond in a factory. Diamond material can be the same, but origin, growth indicators, treatments and market value differ.
Ruby and sapphire Corundum, Al₂O₃ 9 Natural corundum forms in suitable rocks; lab methods include flame fusion, flux, pulling and selected hydrothermal methods. Ruby is red corundum; sapphire covers many other colours. Manufacturing process can affect trace features, not the mineral name.
Emerald, aquamarine and morganite Beryl, Be₃Al₂Si₆O₁₈ 7.5–8 Natural beryl grows in particular geological environments; synthetic emerald commonly uses flux or hydrothermal growth. A lab-grown emerald is beryl. A Zambian-style colour name does not establish natural Zambian origin.
Amethyst, citrine and rock crystal Quartz, SiO₂ 7 Natural quartz grows in rock cavities and fluids; synthetic quartz is commonly hydrothermal. Synthetic quartz can look extremely clean and may require specialist testing to distinguish.
Spinel Magnesium aluminium oxide, MgAl₂O₄ 8 Natural spinel is mined; synthetic spinel can be flame-fused or flux-grown. Some synthetic spinel is sold as a simulant of ruby or sapphire, but spinel is a distinct gem mineral.
Alexandrite Chrysoberyl, BeAl₂O₄ 8.5 Natural alexandrite is a colour-change variety of chrysoberyl; laboratory growth includes pulling, flux and floating-zone methods. Colour-changing synthetic sapphire or spinel can imitate alexandrite without being chrysoberyl.
Tourmaline / natural Paraíba Complex borosilicate mineral group 7–7.5 Natural Paraíba tourmaline is qualifying copper-bearing tourmaline; it is not simply any neon-blue gem. ZGems' lab-grown Paraiba-colour stones are described by their appearance; exact mineral species remains unverified in current listings.
Opal Hydrated silica, SiO₂·nH₂O; generally noncrystalline Approx. 5–6.5 Natural opal precipitates from silica-rich solutions; some synthetic opals use organised silica-sphere production. Synthetic, imitation and composite opal products require clear descriptions; not every opal-like stone has the same structure.
Moissanite Silicon carbide, SiC About 9.25 Jewellery moissanite is generally laboratory-made silicon carbide. A separate material often used as a diamond simulant; it is not laboratory-grown diamond.
Cubic zirconia (CZ) Zirconium dioxide, ZrO₂ About 8–8.5 Manufactured zirconium-oxide crystals, often by a specialised high-temperature melt process. A common low-cost diamond simulant; not diamond, and not the natural mineral zircon.

On mobile, swipe the table sideways to see all columns.

How laboratory gemstones are made

Every manufacturing method starts with the right chemical ingredients and conditions for crystallisation. The method matters because it can affect growth time, production equipment, characteristic inclusions and cost. No method alone establishes a finished stone's quality grade.

1. MaterialPurified inputs and colourants
2. Crystal seedStart the correct structure
3. GrowthControlled melt, solution or gas
4. FinishingCut, polish and possible treatment
5. VerificationIdentify, grade and disclose

Generalised workflow. Some methods do not use a conventional crystal seed; engineered and noncrystalline materials have different stages.

01

Melt growth

Flame fusion (Verneuil)

Commonly used for: Synthetic ruby, sapphire and spinel

  1. 1Precisely formulated powdered raw materials and colour-forming additives are prepared.
  2. 2Powder passes through a high-temperature flame and melts into droplets.
  3. 3Droplets build a growing, rotating crystal boule as the support is lowered.
  4. 4The boule cools and is cut, polished and assessed.

Growth effort: Lower relative production complexity. Fast compared with slow solution-growth methods.

Potential strengths: Reliable colour and scalable production can make genuine synthetic corundum and spinel accessible.

Quality and identification: Curved growth striae, colour banding or rounded gas bubbles may aid identification. Fractures, strain or inclusions can occur.

The lowest-cost growth route does not mean the finished crystal is a fake mineral.

02

Controlled melt growth

Crystal pulling (Czochralski)

Commonly used for: Synthetic corundum, chrysoberyl/alexandrite and some garnet-family crystals

  1. 1Starting chemicals are melted inside a heated crucible.
  2. 2A seed crystal is touched to the melt surface.
  3. 3The seed is slowly raised and rotated, allowing a cylindrical single crystal to grow.
  4. 4The crystal is cooled, examined and cut into gemstones.

Growth effort: Moderate to high equipment and energy requirements. Typically faster growth than lengthy flux programmes.

Potential strengths: Good control of crystal orientation, uniformity and chemistry under suitable manufacturing conditions.

Quality and identification: High-temperature equipment is expensive, and growth defects, strain or colour zoning remain possible.

A premium growth setup alone does not guarantee premium cutting or final appearance.

03

High-temperature solution growth

Flux growth

Commonly used for: Synthetic ruby, sapphire, emerald, alexandrite and some spinel

  1. 1Gem-forming chemicals are dissolved in a molten flux solvent.
  2. 2Carefully controlled cooling or chemical conditions create supersaturation.
  3. 3New gem crystal grows gradually on seeds or in the solvent.
  4. 4Crystals are separated from flux residue, cleaned and cut.

Growth effort: Often high time, material and operating cost. Slow: weeks to months, sometimes longer.

Potential strengths: Can produce convincing crystal growth and attractive colour, including some difficult-to-grow minerals.

Quality and identification: Growth may be slow with limited yield. Flux residues or wispy flux inclusions can be identification clues.

A flux-grown ruby is still synthetic ruby; its higher production effort does not make it natural.

04

Water-based solution under pressure

Hydrothermal growth

Commonly used for: Synthetic emerald, quartz/amethyst, some sapphire and other beryl

  1. 1Nutrients are placed in a sealed high-pressure vessel (autoclave).
  2. 2Hot pressurised water and dissolved chemicals transport the nutrients.
  3. 3A temperature gradient drives dissolved material onto seed crystals.
  4. 4Crystals grow over time, then are cooled, examined and cut.

Growth effort: Moderate to high equipment and operating complexity. Slow, controlled growth; varies widely by mineral and crystal size.

Potential strengths: Very useful for quartz and beryl; produces the actual synthetic mineral rather than a glass imitation.

Quality and identification: Pressure equipment and long growth cycles add cost. Seed plates, growth zoning and special inclusions may help identification.

The exact chemistry, temperature and pressure vary; there is no single universal hydrothermal recipe.

05

High pressure, high temperature

HPHT diamond growth

Commonly used for: Laboratory-grown diamond (carbon)

  1. 1A tiny diamond seed, carbon source and metal solvent/catalyst are placed in a growth cell.
  2. 2The press applies very high pressure and high temperature.
  3. 3Dissolved carbon migrates through the molten metal and crystallises on the seed.
  4. 4The grown rough diamond is extracted, sorted, cut, polished and tested.

Growth effort: High reactor capital and energy requirements. Industrial growth cycles range from days to weeks.

Potential strengths: Produces real diamond; manufacturers can obtain very good colour and clarity with suitable process control.

Quality and identification: Some stones have metal-flux inclusions, growth-sector features or unusual fluorescence. Lab identification needs appropriate equipment.

HPHT may also refer to a post-growth diamond treatment; a treatment is not proof of the original growth method.

06

Chemical vapour deposition

CVD diamond growth

Commonly used for: Laboratory-grown diamond (carbon)

  1. 1Thin diamond seed plates are prepared in a controlled chamber.
  2. 2A carbon-containing gas mixture enters the low-pressure chamber.
  3. 3Energy creates a reactive plasma; carbon deposits on the seeds as diamond.
  4. 4Rough crystals may be further processed or treated, then cut, polished and tested.

Growth effort: High reactor, electricity and processing costs; scalable commercially. Usually repeated growth cycles over weeks, depending on size and quality.

Potential strengths: Produces real diamond with excellent quality possible; the process is highly controllable.

Quality and identification: Growth layers, strain patterns or colour requiring treatment may occur. Only specialist testing reliably establishes origin.

Neither CVD nor HPHT is automatically superior; judge each diamond by documented grading and appearance.

07

Assembly or other materials engineering

Engineered opal and other alternatives

Commonly used for: Some synthetic opal; other laboratory-made decorative gem materials

  1. 1Starting particles or chemical components are prepared.
  2. 2An ordered silica-sphere arrangement or other suitable structure is built.
  3. 3The material is consolidated and may be stabilised or processed.
  4. 4It is finished and sold with the correct material and origin description.

Growth effort: Method- and product-dependent. Depends on precipitation, settling, consolidation and other operations.

Potential strengths: Can reproduce optical effects such as play-of-colour in appropriate synthetic or engineered materials.

Quality and identification: Products differ in composition, binders and durability; not every colourful manufactured stone is synthetic opal.

This is for education only; it does not change the ZGems Natural Opal collection.

Important: the manufacturing examples above represent recognised industry technologies. They are not confirmation of which method any particular ZGems supplier used. If a product's precise growth method matters to you, request the available manufacturing declaration or gemmological report for the exact item.

Gem-by-gem: natural material, lab method, value and quality

Compare commonly encountered gemstones and jewellery alternatives. The listed lab methods are possible or common industry routes, not claims about the production history of every product.

Gem or material Laboratory route Typical manufacturing-cost picture What affects quality Learn or shop
Diamond HPHT or CVD; both make diamond High-capital, scalable commercial production; no universal per-carat cost Colour, clarity, cut, growth/colour treatments, report and inclusion type Lab-grown diamonds · Diamond guide
Ruby (red corundum) Flame fusion; flux or pulling also possible Flame fusion often lower manufacturing effort; flux typically slower and costlier Red hue, transparency, inclusions, cutting, treatments and disclosed growth method Ruby collection · Ruby guide
Sapphire (blue, yellow, purple and pink-orange) Flame fusion; also flux, pulling and some hydrothermal growth Ranges from relatively economical flame fusion to much higher-cost specialist growth Hue, tone, saturation, crystal defects, cut and treatment disclosure Gemstone collection · Sapphire guide
Emerald (green beryl) Hydrothermal or flux Typically time- and equipment-intensive compared with common flame-fusion corundum Green colour, transparency, fissures/inclusions, durability and coatings/fillings Emerald collection · Emerald guide
Quartz (amethyst and citrine) Hydrothermal Commercially established; price depends on scale, crystal size and quality Colour consistency, twinning/growth clues, treatments and material identification Educational example — ask about sourcing
Spinel Flame fusion or flux Flame fusion often economical; specialist flux generally more demanding Whether genuinely spinel rather than a sapphire/ruby imitation; colour and clarity Educational example — ask about sourcing
Alexandrite (chrysoberyl) Pulling, flux or selected other methods Specialist production can be relatively costly; natural fine alexandrite can be very expensive True chrysoberyl identity and strength of colour change in different lighting Educational example — ask about sourcing
Aquamarine and other beryl Some hydrothermal synthetics exist; less common jewellery supply Market supply varies; not all advertised 'lab aquamarine' is synthetic beryl Verify the underlying beryl mineral rather than relying on blue colour alone Educational example — ask about sourcing
Natural Paraíba / Paraiba-colour Natural Paraíba is tourmaline; no verified lab-tourmaline growth method claimed for ZGems Not directly comparable until the precise laboratory-grown material is documented Identification first: actual species, origin claims, treatments and test reports Paraiba-colour range · Important distinction
Opal Certain engineered/synthetic opals are made by silica sphere methods Strongly dependent on composition, binder, pattern and manufacturing technique Play-of-colour, stability, structure and whether natural, synthetic or imitation Educational example (no change to existing Opal products or collection)
Moissanite / cubic zirconia Synthetic silicon carbide / zirconium oxide melt growth Often less expensive than comparable diamond jewellery stones, but not comparable mineral identities Confirm they are simulants rather than lab-grown diamond; check wear and optical differences Educational diamond alternatives — not a claim of current ZGems stock

Swipe horizontally on mobile for all columns. Educational examples do not imply current ZGems inventory.

Growth-process cost and quality comparison

There is no reliable universal “cost per carat” chart across these methods: raw material, equipment, power prices, yield, growth time, size, colour, cutting losses, factory scale, treatments, certification and retail margins can each change the economics. Public production costs are often proprietary. The comparisons below are therefore qualitative manufacturing-effort guides, not Australian retail price quotes.

Method Typical growth effort Main cost drivers Example material Quality notes
Flame fusion Relatively low Often efficient and scalable Common synthetic ruby, sapphire and spinel Potential curved growth lines or bubbles; still genuine synthetic mineral
Crystal pulling Moderate–high Controlled melt and seed growth Corundum, alexandrite/chrysoberyl Can provide uniform crystals; defects and strain remain possible
Flux growth High Slow growth; specialised solvent and control Emerald, ruby, sapphire, alexandrite Flux inclusions can occur; greater cost does not guarantee higher gem grade
Hydrothermal Moderate–high High-pressure vessel; controlled solution growth Quartz, emerald and other selected synthetics Often excellent quality; chevron zoning or seed remnants may occur
HPHT diamond High capital / variable unit cost Very high-pressure equipment; industrial cycles Lab-grown diamond Diamond quality varies; possible metal-related inclusions and growth zoning
CVD diamond High capital / variable unit cost Vacuum/plasma reactors and post-growth processing Lab-grown diamond Diamond quality varies; treatment and strain patterns may matter

What usually makes a stone cost more?

  • Verified mineral identity, origin and disclosure
  • Desirable, attractive colour and visual brightness
  • Better cutting, polish and favourable proportions
  • Clarity, inclusions, larger usable rough and lower yield
  • Slower crystal growth, more rejected rough or extra treatments
  • Independent laboratory reports and traceable supply
  • Demand, rarity and brand or retailer margins

What a growth method does not tell you

  • Not automatically more brilliant: cut and optical properties are key
  • Not automatically more durable: mineral and treatments matter
  • Not automatically more valuable: natural scarcity and resale markets differ
  • Not automatically inclusion-free: each process can leave its own features
  • Not automatically untreated: some stones are treated after growth
  • Not proof of origin: visual appearance alone cannot identify growth history

Natural versus laboratory-grown: practical price and value trade-offs

Natural stones may attract a rarity premium when they have desirable colour, clarity, size and well-supported provenance. Prices vary enormously: common natural quartz is not necessarily more expensive than a specialist-grown crystal. Laboratory-grown stones often offer more size or visual quality for the buying budget, particularly for widely produced materials, but their resale markets and price history differ from natural gems. Simulants can be even less expensive because they are different materials, not because they are inherently badly made.

For laboratory-grown diamonds specifically, both HPHT and CVD can produce high-quality diamond. A seller should not charge a premium solely for one growth acronym without showing meaningful differences in the actual stone and its report. Compare comparable cut, colour, clarity, carat, treatment and seller service.

How to assess quality and verify a gemstone

  1. Confirm the actual material. Ask whether the item is diamond, corundum, beryl, quartz, spinel, chrysoberyl or another correctly named material.
  2. Confirm natural, synthetic or simulant status. A colour-style name is not a substitute for material identity or origin disclosure.
  3. Ask for the production method only when supported. HPHT, CVD, flame fusion, flux and hydrothermal are technical claims requiring supplier information or suitable gemmological examination.
  4. Check colour, cut and size. Inspect hue, tone, saturation, transparency, millimetre dimensions, surface finish and brilliance.
  5. Ask about inclusions and treatments. Heat treatment, colour modification, filling or coatings may affect appearance, care and value.
  6. Read reports carefully. The issuing laboratory, report type, identifying details and any laser inscription should match the exact item. Not every stone is supplied with an independent report.
  7. Discuss durability in jewellery. Mohs hardness measures scratching, not resistance to chips. Some gems require protected settings or specific cleaning precautions.
  8. Compare the total purchase. Include the stone, design, setting, labour, shipping, returns and any documentation—not simply a price per carat.
Special note for ZGems: The store lists laboratory-grown diamonds, rubies, sapphires and emeralds, as well as a lab-grown Paraiba-colour range. The Paraiba-colour term refers to appearance; the exact underlying gem species is not independently verified in the current listings. Do not treat those listings as verified laboratory-grown tourmaline, and do not assume any individual product was made with a specific process without documentation. See the Paraiba-colour guide.

Frequently asked questions

Is a lab-grown ruby or sapphire a real gemstone?

Yes, when the material is correctly identified as synthetic corundum. It is not naturally formed, but its mineral identity is corundum. By contrast, a red synthetic spinel sold to imitate ruby is a different mineral.

Is a lab-grown diamond identical to a natural diamond?

Both are diamond in composition and crystal structure and share essential physical properties. Their origin, growth patterns, possible treatments, pricing and documentation are different; expert testing can distinguish them.

Which is better: HPHT or CVD?

Neither is universally better. Both can produce excellent diamonds and both can produce stones needing extra treatment or showing growth-related features. Compare the specific finished diamond and supporting report.

Why is flame-fusion sapphire often cheaper than flux-grown sapphire?

Flame fusion is an established, efficient melt-production process. Flux growth is generally slower and can consume more production effort. A higher production cost does not automatically improve the mineral's durability or the finished gem's beauty.

Does a lab-grown emerald have the same hardness as natural emerald?

Correctly identified synthetic emerald and natural emerald are both beryl with similar intrinsic hardness, but the inclusions, fissures, treatments and cut can affect how safely the finished stone wears.

Can you identify the manufacturing method from a photograph?

Not reliably. Laboratories may use microscopy, spectroscopy, UV fluorescence or photoluminescence and other specialist techniques; some stones need multiple tests.

Are moissanite and cubic zirconia lab-grown diamonds?

No. They are different materials that can resemble diamond. Synthetic moissanite is silicon carbide and cubic zirconia is zirconium dioxide.

Do growth methods determine retail price or resale value?

Not by themselves. Supply, quality, size, reports, market conditions and margins matter. Published process descriptions are not a substitute for comparable, current seller quotations.

Are all ZGems stones certified for growth method?

Do not assume so. Check the individual product description and ask which origin, material and process documentation is actually available for the selected stone. We avoid claiming a specific process without suitable evidence.

References and further reading

These sources explain industry science. They do not verify the origin or manufacturing process of an individual ZGems product.

Choose a gemstone by colour ↗ Clarity & colour explained ↗ Compare gemstone cuts ↗ Gemstone education hub ↗ Paraiba-colour vs Paraíba tourmaline ↗ Ask about a specific gemstone ↗

Educational content, not a product certificate, independent appraisal or price quotation. Individual stone descriptions and supplier information take precedence over industry examples.