“DOWN THE HILL” YARROW CREEK, NEAR GLEN INNES NSW AUSTRALIA

LIST OF ALL BLOG ENTRIES TO DATE

10.2 and 4.9 carat sapphires

Thanks to Google Earth. "Down the Hill" is in the centre

Many visitors to Glen Innes have enjoyed a day’s fossicking at “Down the Hill”, both on our Wednesday Baptist Church trips and during Minerama. I’ve written about the place in two previous blog entries (Quartz at Down the Hill and The Big Sapphire). Several videos have also covered the area (one, two and three). Click on the links to go there. 

                      “Down the Hill” lies downstream of “Through the Fence” and upstream of “Underground River”.

Down the Hill is an area with many rocky outcrops and, most notably, an abandoned channel through which the creek only flows in flood. At one time this was the most productive area, but the old diggings have mostly filled with sand and no-one seems too keen to spend the day removing it when they could search among the rocks. At the lower end of the channel the wash was at least two metres below the overlying sand. The last we saw of it, there was lots of black jack and    

Cliff O'Brien digging in the old channel 1998

presumably gems, but we were beaten by inflowing water and finally by a flood which filled up the hole with sand. Maybe one day, during a drought, fossickers will get another chance to experience the thrill of working this spot.

At some time, probably in the 1960’s, a small mining operation operated at Down the Hill. There was the remains of a shed or hut when I first visited the place in 1988 but hardly any sign of actual mining. This was on the flat immediately below where we parked. The only other sign of previous visitation was a Tamworth 1 pint milk bottle I found in the creek just below old hut site.

4.3 carat sapphire, 11.6 carat zircon (July 2008)

One day's small finds - December 2009

The gemstones are the usual ones for Yarrow Creek – sapphire, zircon, pyrope garnet, the occasional topaz and enstatite and, of course, quartz. My one and only cuttable ruby came from here, as well as my largest sapphire, best dog’s tooth crystal and biggest quartz 

0.3 carat ruby

Snowing July 2008

crystal. This is more a    reflection of the sheer quantity of wash we found than its superior  quality.

It’s a place I have never tired of visiting.

  https://johnsbluemountainsblog.blogspot.com/2013/12/links-to-all-blog-entries-and-relevant.html All Blue Mountains blogs and videos

https://johnsnewenglandminerals.blogspot.com/2013/12/list-of-all-blog-entries-to-date.html

All New England and other Geology blogs and videos

https://www.blogger.com/blog/posts/1325599670344725659?pli=1

Limestone Caves of NSW

https://www.blogger.com/blog/post/edit/1147003616874115974/2430103125095714141

Song Studies. Bible studies based on hymns and songs

https://www.blogger.com/blog/posts/1515863000684737715

Shoalhaven District Geology.

Snowing: July 2008 - the same day as the gemstone group above was found! July 2008

MISCELLANEOUS MINERALS FROM YARROW CREEK NEAR GLEN INNES NSW

MISCELLANEOUS MINERALS FROM YARROW CREEK 

NEAR GLEN INNES NSW

All gem hunters in Yarrow Creek soon become familiar with the most abundant minerals to be found there. Quartz, as always, leads all the rest in quantity. Mostly it's waterworn, but the occasional near pristine crystal turns up. 

Along with the quartz, orthoclase felspar is sometimes seen. No doubt, both the quartz and felspar are derived from veins in the granite, which outcrops in most places fossickers go. 

Black spinel (pleonaste, blackjack), corundum (a high proportion of which is gem quality sapphire), zircon and pyrope garnet are found everywhere. Sometimes the vagaries of the currents during floods cause the zircon and garnet to be concentrated separately, though always with spinel and corundum.

The less common minerals,but still common enough to be found every visit or so, are enstatite and schorl tourmaline. Topaz is found once in a while, perhaps one or two pieces in a year of regular weekly outings. Once a blue specimen was found. Just once a pale specimen of ruby  turned up in my sieve, and this has already been illustrated in the blog entry on pink sapphires.

Finally, there are the miscellaneous things that turn up, which, while not all one-offs, will bother most 

Ilmenite

fossickers trying to identify them. Ilmenite is reasonably common but not normally noticed. It occurs as cylindrical, metallic looking lumps, though why it is in this form I do not know .

carnelian 3cm across

Silicified wood 11cm long

I've seen the occasional piece of agate, though I failed to photograph one. The photo of the specimen of orange chalcedony (carnelian) is a one-off, as are the silicified wood and rutile. The chalcedony would be related to the silicification of wood trapped beneath the nearby basalt flows, though I would have expected them to be more abundant. 

Rutile 2cm long

The specimen of rutile is an unexpected find, mainly because I have never seen another. Such a vast amount of rutile has accumulated in heavy mineral deposits along our coasts that I would have expected more to turn up in creeks like Yarrow which drain in that direction.

Lastly, here is a specimen about which I know nothing. It was found amongst the sieve concentrates, so it's reasonably dense. It doesn't look like the rest of the corundum, which I thought it was initially. It remains a mystery mineral.

Unknown mineral

Check my gem hunting videos from around Glen Innes here . 

https://johnsbluemountainsblog.blogspot.com/2013/12/links-to-all-blog-entries-and-relevant.html All Blue Mountains blogs and videos

https://johnsnewenglandminerals.blogspot.com/2013/12/list-of-all-blog-entries-to-date.html

All New England and other Geology blogs and videos

https://www.blogger.com/blog/posts/1325599670344725659?pli=1

Limestone Caves of NSW

https://www.blogger.com/blog/post/edit/1147003616874115974/2430103125095714141

Song Studies. Bible studies based on hymns and songs

https://www.blogger.com/blog/posts/1515863000684737715

Shoalhaven District Geology.

The mineral we all want to find: 16.8 carat blue sapphire

ENSTATITE FROM YARROW CREEK NEAR GLEN INNES NSW

ENSTATITE FROM YARROW CREEK 

NEAR GLEN INNES NSW

In my first years of gem hunting in Yarrow Creek I occasionally came up with pieces of a mineral which looked like black spinel but differed in that they showed a green to orange-brown colour when held up to the sun. The best specimens were transparent and gemmy.

As I had done before with specimens of pink sapphire, I sent a few samples to Hylda Bracewell, the highly regarded gemmologist then living in Torrington NSW. Hylda concluded that they were enstatite with some examples approaching hypersthene in their properties.

These minerals are members of the pyroxene family, which are commonly found in basic to ultrabasic igneous rocks and some metamorphic rocks. Their chemical formula can be summarised as (AB)₂Si₂0₆, where A and B are metals. In the family of which enstatite and hypersthene are part, the metals are magnesium (Mg) and iron (Fe). Pure enstatite contains no iron, only magnesium, hypersthene contains both iron and magnesium.

 An important question to be answered is this: where does this mineral come from? Not from the local granites, which appear to contain no pyroxene minerals. Not from the same volcanic source as corundum, zircon and spinel, since it is not found with them in most local creeks. Perhaps from the gabbro dyke which outcrops just upstream from Garnet Corner, some other dyke yet to be identified, or from xenoliths in the granite.

These minerals are not especially hard or dense, but hard and dense enough to end up in the sieve centre along with the sapphire, zircon, garnet and spinel which make up the bulk of the concentrate. Enstatite has a hardness of 5.5 on Mohs’ Scale and a specific gravity of 3.2 – 3.3. They can be cut as gems but need to be protected from undue wear. The colours are not particularly attractive and difficult to see in a set stone.

Despite its shortcoming as a gemstone, a piece of rich green enstatite is a good find and many amateur cutters would like to work on a Yarrow Creek stone if they could find one.

Why not check out my You Tube channel here  where you can view gem hunting, mining and general geology videos. 

https://johnsbluemountainsblog.blogspot.com/2013/12/links-to-all-blog-entries-and-relevant.html All Blue Mountains blogs and videos

https://johnsnewenglandminerals.blogspot.com/2013/12/list-of-all-blog-entries-to-date.html

All New England and other Geology blogs and videos

https://www.blogger.com/blog/posts/1325599670344725659?pli=1

Limestone Caves of NSW

https://www.blogger.com/blog/post/edit/1147003616874115974/2430103125095714141

Song Studies. Bible studies based on hymns and songs

https://www.blogger.com/blog/posts/1515863000684737715

Shoalhaven District Geology.

Facetted enstatite 1.5 carats