How to Distinguish Between Synthetic Citrine and Natural Citrine

The difference between natural and synthetic citrine How to tell the difference between synthetic and natural citrine.
It is more likely that natural citrine is impure because of the external forces that affect its natural growth. These contaminations may be of different colors or shapes of inclusions. It is generally possible that synthetic citrine has no such inclusions.
Citrine may have the inclusion of cotton-like, cloudy, or ice crack, or other imperfections, e.g. liquid-gas inclusions, coexisting minerals or fissures. Very little of high quality natural citrine is pure and free of impurities. Synthetic citrine can be highly purified since it is produced under controlled conditions, and usually has no visible inclusions.
Glass is typically used to create synthetic citrine and can have tiny bubbles in it. The most convenient method to test is by putting the fake citrine in front of an item such as a piece of paper that has text or lines. Turn the stone over and see what is written or drawn underneath it. Due to the homogenization of glass, you will only visualize one picture of the text or lines. But since citrine is a heterogeneous material, it will have doubled images of the text or lines as it rotates.
Natural citrine which has been grown over a long period in the natural environment usually contains gas-liquid inclusions, cloudy matter, coexisting minerals, or fissures. An unblemished natural citrine is quite uncommon and in most cases, it is suspicious. The quantity and size of these inclusions are at times hard to see by the bare eyes and need a 20x magnifying glass to be examined.
The natural citrine possesses quick heat conductivity. It is cool at first when it is in your hand and then it will adjust to the body temperature after some time. At first glance, synthetic citrine produces a warm feeling.
Citrine is a birefringent natural material. When you hold citrine on one of the locks of your hair and you turn the stone in one direction you find that there are two images. This is not observed by synthetic citrine.
Hardness Test:
The hardness of citrine is 7 in the Mohs scale and that of glass is approximately 5.5. A scratch upon glass with citrine will not leave a mark, but a scratch made on glass will leave a scratch.
Thermal Conductivity Test:
Position the thermal conductivity tester to the green (level 4) and test the gemstone. Natural citrine will be increased to yellow (level 2), and in case the area is large, the natural citrine will be increased to yellow (level 1). This is not observed in synthetic citrine.

The process of manufacturing Synthetic Citrine.
It is possible to grow a-quartz crystals artificially under high pressure, a-quartz dissolves in alkaline solutions at high pressure, and the crystal structure is more complete with fewer inclusions, twins and voids. The solubility of a-quartz reduces with a drop in the temperature enabling the crystals of a-quartz to be produced using sodium hydride or sodium carbonate solutions. Synthesis pressure is 16.5 MPa with a temperature of 400 deg C and the growth rate on (001) base plane is 1.27 mm/day. The electronics industry, ultrasonic generators, and optical instruments, as well as in the analysis equipment, typically make use of synthetic quartz.

High-lead glass Artificial citrine or artificial high-lead is made by mixing 24% lead oxide with normal silica-based glass. This produces artificial quartz that is of much similar brightness and transparency as natural citrine.