How to Extract 99% Pure THCA “Diamonds”

Diamonds, otherwise known as crystalline tetrahydrocannabinolic acid (THCA), have started to become more popular in the cannabis industry. Whether the diamonds are smoked or added to flower, some people are gravitating to purer products across categories, and 99 percent THCA is grabbing attention. Although developed from and for the West Coast American adult use market, the true purpose may lay in the medical market by segregating the purest molecule for targeted treatments. But how are these diamonds made?

Diamonds have unique colorations and clarity that are derived from terpenes and the purity of the crystalline structure. These unique characteristics show the quality of the crystals; the more yellow/gold color means more terpenes are present, and fogginess or lack of clarity in the crystals means there is solvent present. High clarity and a lack of color is a sign of a high potency crystal; any other characteristics will diminish the potency.

THCA diamonds can be created from any non-decarboxylated cannabis oil, whether it’s crude oil made from trim or live resin oil derived from fresh frozen flower. It’s much easier to begin nucleation with an oil that has most undesirables removed (e.g., fats and waxes), so winterize the oil before you begin. Nucleation is when atoms begin to bond together due to reaching a specific temperature called the solidification temperature. Starting with the solvent and working our way to the crystal, let’s explore the best methods to create the finest diamonds.

Anthony DeMeo

Liquid Petroleum Gas Extraction

We’ll go through the typical method of creating THCA diamonds using liquid petroleum gas (butane/propane) extractions. When performing your extraction, it’s important to chill your jacketed extraction system to -50oC or colder. Then, reduce the pressure in your system to -30 mmHg, or as low as you can go based on elevation, using your vacuum pump. Perform your extraction as normal but maintain a ratio of solvent to biomass between 6:1 and 10:1. If you have a dewaxing column, you can utilize this to assist in further removing undesirables. Recover most of the solvent, or about 90 percent, at 18oC–this will preserve your terpene profile.

The deviation from routine extraction begins here. Once the solvent is recovered, transfer your solution (cannabinoids/solvent/terpenes) to a pressure-rated crystallization vessel, which can be any vessel that handles pressure and has a pressure gauge, pressure release valve, and a vent valve. Modified mason jars or stainless-steel reactors are most often used depending on scale. Once the vessel is filled, tightly close and chill it to -75oC or colder for 48 hours. After this time, remove the vessel from the cold environment, open the vent valve, and allow the solution to reach room temperature. This will remove approximately one-third of the remaining solvent.

Low and Slow

Close the vessel and very slowly increase the temperature to 25-35oC over the course of 5-30 days. This low and slow method will encourage more nucleation due to increased temperature and pressure and larger crystal growth. Once the desired diamond size is achieved, pour off the remaining layer that’s comprised primarily of terpenes. This terpene layer can be poured into a secondary crystallization vessel with the steps repeated to allow for further precipitation of THCA. The described process is called “diamond mining” in the recreational market.

Without additional processing, it produces a more full-spectrum product called a high-terpene full-spectrum extract (HTFSE). This HTSFE is comprised of high potency THCA crystals with a layer of terpenes. On average, HTFSE is about 70 percent THCA and 15 percent terpenes. Each time you pour off the terpene layer and leave the crystals behind, the potency increases. Eventually, the HTSFE will have small amounts of terpenes present with large crystals, or many small crystals, and it will be ready for the final purge.

Once you’ve achieved your desired crystal growth, purge the residual solvents from the terpene layer and crystals using a large glass (e.g., Pyrex) dish that allows you to create a thin layer of terpenes, maximizing the surface area. Put the filled dish and crystallization vessels into a vacuum oven using a drying temperature between 18-30oC. A vacuum of -15 to -20 mmHg should be used to assist the purging process. At the end of this process, you will have produced a high potency THCA diamond. The THCA content of these crystals can be as high as 99 percent but can fluctuate depending on residual solvent and terpene content.

After the Purge

Further processing of these diamonds can be performed after the purge. You can continue to grow larger diamonds utilizing super-saturated hexane and to improve the clarity of your diamonds using chilled pentane washes. If you intend to produce a THCA crystalline with above 99 percent purity, you will need to perform these washings. Be careful, though, as too much solvent or solvent that is too warm will dissolve your THCA. These techniques are for you to further explore and expand your understanding of forming THCA diamonds.

Besides simply smoking THCA crystals and/or mixing with flower, formulation specialists may want to combine these diamonds with terpenes or other cannabinoids to create a unique treatment for medical cannabis patients. Preliminary research into THCA has shown this cannabinoid possesses anti-inflammatory, neuroprotective, anti-emetic, and anti-proliferative properties. Combining THCA with cannabinoids like cannabinol (CBN) and terpenes that promote relaxation, such as linalool, could assist in recovery or rest. Individuals with nausea may want a capsule or tincture that has a ratio of THCA and cannabidiol (CBD), another cannabinoid with potential anti-emetic effects, and some myrcene to help alleviate their discomfort. No matter how you consume cannabis, the idea is to treat something that ails you physically as well as mentally.

Creating unique mixes from THCA is precise chemistry that will spawn thousands of future products. While THCA is a useful cannabinoid on its own, the synergistic effects of cannabinoids and terpenes are not to be underestimated. Isolating cannabinoids to their purest form, such as THCA diamonds, and recombining them with terpenes is the first step in creating treatments that target specific symptoms. Hopefully, improving processing techniques and purifying cannabinoids will help lead to future cannabinoid-based research so we can begin manufacturing cannabinoid-based drugs for treating specific ailments, thereby moving away from the anecdotes that we have today.

This article was written by Michael Sassano and Anthony DeMeo of Somai Pharmaceuticals. Anthony DeMeo is Co-Chair of the Extraction & Manufacturing Department at Oaksterdam University. The piece first appeared in Issue 16 of Extraction Magazine under the title “These Diamonds Likely Won’t Last Forever.” Reprinted with permission. Link to a pdf of the issue here.


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