Using Oxalic Acid to Clean Idaho Star Garnet Rough

Somehow, the book has tripled in size and a new "first draft" is finally done! Now, it's time to take a little break, get the book cover designed and start cutting some gems. 

Star garnets, when found, almost always have a thick crusty layer of limonite on them. Before a gem-cutter can assess whether a crystal is worth cutting, this rind has to be removed. I showed a quick method that works great for single pieces in the last posting. If you have a larger parcel, acid might be the way to go.

Many mineral collectors use oxalic acid to clean quartz and other crystals. I'll be showcasing how well this method worked for my garnet. But first, I have to mention- this is dangerous stuff. Oxalic Acid is highly toxic and corrosive. If you're at all uncomfortable using chemicals and acids- DO NOT try this! Before using any chemical- always read the MSDS (Material Safety Data Sheet). They're easily found on google as are other mineral collector's write-ups about using this method. What's needed:

Ingredients:

Distilled Water

Oxalic Acid (also known as “Wood Bleach”)

Iron-Oxide coated Garnet Crystals

Tools:

MSDS

Crock Pot

Good Quality Plastic Container (that fits inside the crock pot)

Measuring Cup

Gloves (Rubber or anything acid-proof)

Safety Glasses

Plastic Spatula or (preferably) Tongs

About 1.5 pounds of garnet crystals.

I also included some non-star garnet crystals (lower right) that were collected near
Emerald Creek. These will never cut asteriated gems and are sometimes found on ebay.

The container of oxalic acid says to use 12 oz. to 1 gallon of water. I mixed about half that amount: 6 oz. for half a gallon of distlled water.

Even though I bought my crock-pot for $2 I don't want to ruin it with acid. If there is a tiny crack or chip in the enamel, the acid will eat its way through. Instead, I'm heating pure water in the pot and then putting it in the plastic container with the acid-water mixture and the crystals.

Heat speeds up the reaction with the acid and cuts down on the time spent in acid. I had the crock pot setting on low and checked up on it periodically.

After a couple of days, a dark, greenish-brown tint developed in the inner container.

The acid ate away at the majority of the outer skin. Enough, so that I know how
and where to trim them. Some pieces may still benefit from a second soaking.

Top row consists of the non-star garnet crystals. Looks like they
 have a somewhat different type of acid resistant mineral coating.

After taking the crystals out of their container with plastic tongs, I rinsed them with lukewarm tap water and then soaked them in fresh water. Just to be safe, I added a little baking soda into the water in order to neutralize any residual acid. I've heard that the acid in the container can be reused. That's where heating it in the separate containers comes in handy. I can pop the lid on, clearly mark it, and put it far out of reach of any children and curious cats. Much better than leaving it in an unsecured crock pot. If you have no intention of re-using the acid- DO NOT POUR IT DOWN THE DRAIN OR ONTO YOUR YARD. First, neutralize the acid with baking soda or lime. Also, remember- NEVER ADD WATER TO ACID- it will splash you.

Feel free to leave comments about using this method. This is the first time I tried it and I welcome any additional tips. I've been restoring an old cabbing machine and am working on an article on “how to detect asterism” in rough garnet. Also, I've been doing lots of locality research and will be showcasing some interesting findings. Lots to look forward to in the coming months!

How to Clean Star Garnet Rough

Larger star garnet crystals have a tendency to be encrusted in a thick layer of rusty iron oxide. It can be tough to remove and there is no way to tell if a crystal is even worth cutting unless this layer is removed.

This large crystal fragment barely has any garnet peeking out. I chose

 this piece because I thought I saw some silk on the surface.  A penny is 

provided for scale. The preying mantis volunteered his modeling services.

The use of oxalic acid is a well known method for removing iron oxide staining from quartz and I've heard it recommended for star garnet crystals too. Commonly known as "wood bleach", most hardware stores carry it in stock. The downside to oxalic acid is that it is corrosive and toxic. I've been avoiding cleaning my crystals with this method since I share my workshop with a very inquisitive Siamese Cat. Just like a small child- I know he'll find a way into this potential toxic garnet stew.

Recently, I heard of a much easier suggestion- a brass bristle brush. Steel might work too. I had neither. However, I am restoring a rusted-out cabbing machine and do have a rust/paint stripping abrasive wheel (manufactured by 3M) that fits into a hand power drill. Here are the results:

 The same crystal face. Rust is nearly all gone. It worked!

A very silky portion of the crystal. This one is a cutter.

This is a great method for a peek into your garnet rough- especially if you don't have a cabbing machine setup. I did test for asterism with the "oil test" and discoverd that this crystal will yield some brightly starred gems. Has anyone tried the brass or steel brush method?

Stewart's Gem Shop of Boise, Idaho along with a writing update

Taken from the Stewart's Gem Shop website- this is the nicest image of star

 garnets I've yet found. These 6-rayed garnets are all of the highest grade.

August and September saw a whirlwind of activity that left little time for updating the blog. Tough to believe that nearly two months have passed since my last blog entry.

I managed to complete another road trip to the Idaho Panhandle National Forest and went searching for rough star garnets with some new friends. We found some incredible material! As the weather gets colder, I'm looking forward to cutting some of the silky, raspberry colored pieces of rough. Look for a future blog entry showing the process of cutting. Hopefully, the stones will display the elusive 6 rays!

As for the writing of the book, I'm working on the second draft of the book and the goal is to complete it by the end of the year. During the summer I visited some beautiful locales, met many wonderful people and uncovered a plethora of information. There has been a wonderful process of discovery along the way and I'm amazed at how much the narrative has changed and grown from my initial outline.

The beautifully landscaped entrance to the well-kept shop near downtown Boise.

Central to the story of Idaho Star Garnet is the Stewart Family. During the 1950s, Dudley Stewart became enamored of the stone and was the first to figure out how to reliably cut the garnet crystals so that they would display stars. Over the next couple of decades he became a constant promoter of the star garnets of Idaho and was instrumental in making it the official state gemstone of Idaho. He built up a successful family business around star garnets and other now famous Idaho gem materials. The shop is still run by the Stewart family and during a research trip to Boise, Idaho I had the pleasure of visiting.

Brent Stewart cutting a star garnet on gem cutting equipment originally built by his grandfather.

Brent Stewart, grandson of Dudley Stewart was in that day and graciously shared his knowledge of how star garnets are cut from the rough. Much of the original lapidary equipment hand-built by Dudley is still in service to this day and the photo above shows Brent cutting and evaluating a star garnet sample that I brought to the shop. Many people who have mined at the USFS site bring their rough to Brent for cutting. If you're looking for a quality star garnet gem cutter I can highly recommend his services.

Mining for star garnets in Idaho

Cloaked in secrecy, many gem deposits occur in locales so remote and guarded that few ever reach them.   The opportunity to find quality gem rough for oneself scarcely exists.

One of the exceptions to this rule happens to be located in Northern Idaho. Nestled in the thickly wooded hills in the Idaho Panhandle National Forest is a mining site managed by the US Forest Service known as the Emerald Creek Garnet Mining Area.

For a $10 day-use fee anybody can mine for the day and try their luck in the gem bearing dirt and gravel. I recently visited this site myself. After working my first two buckets of dirt this is what I found:

The stone to the right of center is a flawless,

facet-grade 8.4 carat rhodolite garnet crystal.

Total weight at the end of the day was 8 ounces and it took searching through 20 five-gallon buckets to find this much garnet. While digging and sifting took the most muscle power- it was the washing of the gravel that took the most work.

The result of a day's mining!

Some of the larger crystals found that day.

All your stones must be thoroughly washed since the sticky and rust colored clay clings to any and every pebble possible. It seemed like everyone at the site is after larger sized garnet crystals with the potential to “star” when cut. However, there is other material to find too. Some of the smaller fragments and crystals consist of facet grade rhodolite garnet in a rich shade of raspberry purple.

Expect to work hard and understand that the average found by visitors is 4 ounces. With extreme hard work and a sharp eye, you can probably find close to a pound of material in a full day. For rough material that may cut a star garnet- the best pieces are somewhat larger (1/2”+) crystals of dark garnet. These are easier to orient for an experienced cutter and are said to be more likely to contain inclusions and layers of rutile that produce a good star.

The site is open Friday through Tuesday from Memorial Day (May) to Labor Day (September). For more information on the site (and others nearby) look for the book “Rockhounding Idaho” by Garret Romaine [2010]. Also, I recommend contacting the US Forest Service and calling ahead to make sure the site is open.

I'm interested in hearing stories and seeing photos from the early days of garnet collecting- especially in the Emerald & Purdue Creek areas. Feel free to contact me if you have anything to share.

Introduction

Diamonds... Rubies... Sapphires... Emeralds... Stories of these gems abound in romance and adventure. However, behind these renowned precious gems there lie hundreds more varieties of unique stones. Many are exceedingly rarer than the aforementioned “Big Four” and all have their own stories wanting to be told.

These other gemstones attract the esoteric, the scientists, adventurers and connoisseurs amongst us. Oftentimes, the histories they hold and the people they attract hold narratives as fascinating as the more well-known stones.

Garnet is one such gem. In its' most common colors- flashes of red or purple emanate out of a dark background- just like a burning coal. It was known since ancient times to the Greeks and Romans and is still commonly used today as the birthstone for January.

One of the rarest and most unusual varieties is known as “Star Garnet”.

A crystal of garnet, from only a handful of world locales, if cut properly, may reveal a four or six rayed star. The state of Idaho is home to one of the few places in the world where these types of crystals occur. It is both the heartland for star garnets and also home to the only “mine” where anyone can visit and collect crystals themselves.

This blog is dedicated to the progress of my book about Star Garnets: “Chasing the Stars”. As I make further progress, meet interesting people and discover new facts about the star garnets- I plan on updating this blog. Please keep checking back to follow my progress on my book.

Comments, questions and stories are all very welcome!

-Martin