John's New England Minerals and General Geology Blog: dog's tooth

Monday, 6 January 2014

“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

Thursday, 11 July 2013

PRETTY VALLEY DOG’S TOOTH SAPPHIRES

Anyone who has hunted for gems at Pretty Valley near Glen Innes will be aware how frequently corundum crystals and hexagonal plates derived from them are found in the wash. In fact, they are more abundant here than any other place I know. We have always called them dog’s teeth; I’ve heard other call them hound’s teeth. The locality is near the source of Bladey Grass Creek.

The crystals range in size from around 0.5cm in length to over 3cm. Most are opaque and display distinct colour banding when viewed from the side.

Transparent examples are less common and are usually yellow with a blue zone on the outside of the crystal. Doubly terminated crystals are almost unknown and the tips are usually missing. Some display crude twinning parallel to the c-axis.

The source of the PrettyValley sapphires is unknown. As usual, they are associated with abundant zircon and spinel. The schorl tourmaline, topaz and quartz crystals found there are no doubt associated with the nearby granite and are probably derived from Kingsgate-like pipes in the vicinity.

Information on the origin of sapphires in the New England region can be found in many places; the Quarterly Notes (3 and 77) of the Geological Survey of NSW contain good summaries. DIGS references for these are QN003 (1971) and QN077 (1989).