GRAPE AGATE FOR SALE

What Color Is Grape Agate?

Grape agate usually ranges in color from deep purple to a pale, whitish purple. Darker, richer colors are more desirable and fetch higher prices. Some material can be green due to the presence of clay inclusions. Higher quality grape agate can be quite sparkly due to the presence of micro quartz crystals on the surfaces of the orbs!

Outside of amethyst and some fluorite, there are not that many purple minerals in the natural world. It has been reported that the color of grape agate will fade when exposed to a flame, so the purple color is likely caused by a similar process as amethyst. A combination of mineral inclusions and natural irradiation.

Where Is Grape Agate Found?

Grape agate is collected from a 25-square-kilometer area of rugged, jungle-covered mountains in the northern end of the Manakarra mining district on the Sulawesi Island of Indonesia. Manakarra Beach, which is about 10 kilometers south of this area, often gets used as a locality name. The first finds of grape agate were reported as small pieces of float found on the beach that had washed down nearby rivers from the mountains. Prospectors followed these rivers into the mountains to locate the deposits that are now actively mined. Local dealers likely provided Manakarra Beach as a locality at first in order to lead the competition astray.

Grape agates are mined from pockets of blue-gray clay in a weathering andesite bedrock. Local miners work by hand, probing the rock with steel rods to search for these pockets. These pockets are then opened up using hand tools and the grape agate clusters are carefully collected. Typically, the more vibrantly colored clusters are found deeper in harder rock that has not yet weathered: exposure to weathering likely leaches minerals from the grape agates, causing some to lose color.

Some great photos of the mining area can be found here and here.

A New Mineral On The Market?

Grape agate from Indonesia first started appearing on the commercial market in 2015. The deposits were likely known for some time before then. Up until 2015, the Indonesian government banned the export of raw minerals to try and keep lapidary jobs in the country.

How Is Grape Agate Priced/Valued?

When grape agate first started appearing on the market it was astronomically priced: some specimens were priced in the tens of thousands of dollars! As larger quantities have been exported, it is much more affordable today, but the majority of exported material is fairly low quality.

Many factors play into pricing. Deeper purple coloration is more desirable, and thus will be priced higher. Larger sphere sizes will also increase prices. How is the luster and sparkle of the specimen? Most of the low quality material is fairly dull in color, but sparklier ones sell higher! Of course, the size of a specimen is also a primary factor in price.

How Was Grape Agate Formed?

Grape agate is found in small pockets of blue-green clay within a host andesite pillow lava, which formed during the Miocene when lava flowed into cold seawater. Andesite lava behaves differently than basalt in that it is more viscous, so when it cooled many voids remained intact between the pillows. The grape agate was then formed by some type of of hydrothermal event where water deposited silica and other minerals within these voids.

Technical description from IndoAgate.com

"I thought the orbs must have formed on some sort of nucleus but proof of that is not yet evident.

A crossed polar micrograph of a Manakarra thin section cut by Terry Moxon, exhibited a Maltese Cross. According to Terry, this uncommon phenomenon results from twisting of the quartz C-axis during rapid growth of a fibrous chalcedony. This is in contrast to the layered growths of chalcedony which forms by deposition in concentric layers in a void such as with agates.

The chemical analysis and XRD indicate composition of the Manakarra is dominantly chalcedonic quartz (SiO2) with very minor potassium, aluminum, calcium and magnesium which are likely decay products of the original volcanic host rock. The blue-green illite or smectite clay is also typical of the decomposition of a mafic host. In this case, aside from SiO2, only minor Ca/Mg/K/Na/Al was detected (<1%).

The weight percent of trace elements is so low that I cannot comment on which are likely contributors to the rich colors we see in the Manakarra specimens recovered from in situ volcanic host rocks."

Is Fake Grape Agate A Thing?

There seems to be some misinformation that the Indonesian grape agate is fake. It is an entirely natural geological formation! Low-grade material may sometimes be dyed a darker color of purple to increase its value, but we have yet to encounter this.

The talk of fake grape agate probably comes from decorative polished stone grapes manufactured in China that have been occasionally sold under the name grape agate. However, this looks nothing like Indonesian grape agate and would be difficult for even novices to confuse with natural material.

Other Names For Grape Agate?

Grape agate is a fairly new trade name for the mineral, coined around 2016. It is also frequently known as Indonesian Purple Chalcedony, Batu Manakarra, Manakarra Agate, etc. Despite the common name grape agate, it is not technically an agate because it doesn't have banding, but is instead a form of chalcedony.

What Is Grape Agate Used For?

Grape agate is very coveted among mineral collectors simply for its sheer natural beauty. High quality specimens with good color, luster, and large botryoidal formations can be quite valuable. Small clusters or individual spheres are often used in jewelry, and it has become popular with the healing crystal community for promoting "profound peace and tranquility".

Has Grape Agate Been Mined Out?

The grape agate is found over a fairly large area, about 25 square kilometers. he mining is difficult, very labor intensive, and done by hand, meaning only the deposits near the surface are collected. Given the size of the deposits and difficulty in extracting the material, it's unlikely that it will be mined our for some time.