Since 1980, geological prospecting departments have successively conducted prospecting and exploration in Changle County, and discovered sapphire deposits. At the beginning of 1986, Shandong People's Broadcasting Station, Dazhong Daily and other media reported the discovery of sapphire in Changle County. The sapphire placer in Changle County became the first evaluated sapphire placer in Shandong Province, which filled the blank of sapphire mineral in Shandong Province. During the period of 1988, the geological prospecting department focused on the sapphire deposit in Wutu area, and confirmed that the alluvial layer in Wutu area is rich in sapphire and is a large sapphire deposit.
The sapphire mine in Changle County covers an area of 450km2, with a reserve of over one billion carats. It is the largest sapphire mine discovered in China at present, and it is also a rare large-scale sapphire-rich mining area in the world, accounting for more than 90% of the total sapphire reserves in China, mainly distributed in parts of Wutu Street, Qiaoguan Town, Chengnan Street, Giulio Givanni Carlo Taccon Street and Yingqiu Town.
Sapphire in Changle county has the characteristics of large particles, complete crystals, pure and bright colors, remarkable dichroism and many unique gems. The particle size is generally above 1cm, and the weight reaches 15 ~ 30ct (carat), with the largest being several hundred carats. The largest sapphire in Changle County weighs about 760ct (carat) and is known as the "king of sapphire". It has the reputation of "Weifang folk national treasure". It is as crystal clear as a drop of water, shining with charming luster under the light. It is one of the largest sapphires in the world at present.
The main colors of sapphires in Changle County are blue, indigo, green and yellow. Blue sapphire is a representative variety in Changle mining area, accounting for more than 80% of the total output of sapphire, and its color is dark. "Yuanyang Gem" composed of blue and green is a unique variety in Changle County. Changle county also has starlight sapphire series, one is blue starlight, the other is copper starlight, which is divided into six and twelve starlight. Some sapphires in Changle county contain strange inclusions, some are like towering mountains, some are like rushing rivers, and some are like animals with different postures, giving people infinite beautiful reverie. "proud as a peacock" and "Smoke from a Kitchen" are rare and priceless treasures in the world.
Identification method of 1. sapphire
Sapphire is gem-grade corundum. According to the crystal morphology and physical properties of corundum, it can be divided into gem-grade corundum and non-gem-grade corundum under binoculars and polarizers.
The principle of sapphire division:
1) color: bright blue, dark blue, green blue, green, yellow green, yellow and so on.
2) Transparency: transparent or translucent, translucent to opaque for starlight effect.
3) Fissures and inclusions: none or undeveloped, or distributed at the edge of particles.
4) Weight and size: the narrowest part of the particle must be greater than 2mm. If there is starlight effect, the particle weight must be greater than 100mg.
Those that meet the above four conditions are classified as gems, otherwise they are non-gems.
2. Changle Sapphire Mining
1987, Fangshan first discovered and mined sapphire primary ore. Then it gradually developed into placer mining in the low-order gully depression around Fangshan. 1992, the county government formulated the Interim Measures for the Management of Sapphire Mining Areas and the Measures for Unified Exploitation of Sapphire Resources in Changle County, and implemented the management of "three areas and one reclamation" for sapphire mining areas according to the principles of unified planning, rational layout, limited exploitation and comprehensive utilization. In order to ensure the sustainable exploitation of sapphire resources, in 2003, the county government decided to suspend the exploitation of sapphire mine and resume the mining area. At this point, the exploitation of sapphire resources in this county has entered the stage of effective protection, standardized management and orderly according to law.
Physical geography and economic geography conditions of deposit development: Changle sapphire metallogenic prospect area has superior geographical environment and flat and open surface. The hydrogeological, engineering geological and environmental geological conditions are simple and shallow, which is beneficial to open pit mining. The traffic conditions in the study area are superior, close to Ji Jiao Railway, National Highway 309 and Qing Ji Expressway. There are many provincial roads connected with simple highways in the study area, and the transportation industry in the study area is very developed. In addition, the study area is rich in water resources and convenient in power facilities, which can meet the demand of hydropower supply for future exploitation.
Future mining and dressing technical scheme: Changle sapphire mine is mainly divided into two types, one is placer mine and the other is primary mine. For sapphire placer, because the mineral composition of the ore is simple, mainly gravel and calcareous nodules, and the content of heavy minerals in the mineral composition is small, only sapphire and corundum are valuable in the ore, and other heavy minerals are basically of no recycling economic value; At the same time, sapphire is mainly used for decoration, the available particle size is above 2.5mm, and other particles are coarse.
In view of the above characteristics of sapphire placer and the requirements for sapphire separation granularity, Changle sapphire placer is an easy-to-select mineral with simple beneficiation method and simple beneficiation operation flow. The recommended industrial development and mineral processing production process is shown in Figure 2-7- 1.
Figure 2-7- 1 Recommended mineral processing technology for sapphire production in industrial development
As for sapphire primary ore, because sapphire primary ore occurs in Neogene basalt, the rock types are mainly olivine basalt and kyanite, and the ore-bearing rock mass contains a large number of deep inclusions-lherzolite, dunite, peridotite and so on. The ore-bearing rock mass has obvious characteristics of green peridotite inclusions, so the ore-bearing horizon is easy to identify. The main purpose of mining sapphire primary ore is to find the ore-bearing layer, and at the same time, because the depth of the ore-bearing primary rock is shallow, open-pit mining is adopted, and sapphire/corundum ore is selected after crushing the primary rock.
3. Processing technical performance of sapphire
Sapphire processing is mainly cutting and honing, which belongs to high-tech technology. The finished product must have beautiful color, good optical effect and the highest economic value. Therefore, sapphire with light color and good transparency should be processed into faceted gemstones; Sapphire with dark color and poor transparency should be processed into plain gemstones. At the same time, we should also pay attention to directional processing. The main facet of a faceted gem must be perpendicular to the C axis, so that the processed gem will be pure blue, otherwise it will be blue-green or blue-green, which will reduce the quality and price of faceted gems. The bottom surface of the plain gem must be perpendicular to the C axis, and the long axis direction of the oval plain starlight gem must be parallel to one of the horizontal axes of the crystal, that is, the A axis or the B axis, so that the center of six or twelve starlights will be in the center of the plain gem, otherwise the starlight center will be biased to one side of the gem, or the starlight of the gem will be asymmetric, or even starlight will not be generated, which will greatly reduce the quality and price of the plain gem and even become waste.
199 1 The former Seventh Geological Team of Shandong Bureau of Geology and Mineral Resources conducted processing tests on 10 sapphire rough stones and 6 sapphire rough stones with starlight effect in the study area (Table 2-7- 1), with the highest output of 53.5 1% and the lowest output of 6544. The output varies with raw materials, processing technology, processing conditions, processing methods and other factors, and is not a fixed constant.
Table 2-7- 1 sapphire processing test
(According to the former Seventh Geological Team of Shandong Bureau of Geology and Mineral Resources 199 1)
4. Changle sapphire deep processing
The first is the processing of sapphire semi-finished products. Since 1990, there have been semi-manual and family-workshop gem processors in Changle County. By 1995, the county processed 65,438+500,000 carats of precious stones every year. Because of the small scale and low grade of jewelry processing in Changle County, its added value is also quite low. To this end, the county party committee and the county government formulated and promulgated the Opinions on Further Accelerating the Development of Jewellery Industry in the County, and organized processing personnel to study and train outside the province and abroad to improve the technical level of gem processing. After 2005, the number of sapphire processing enterprises in the county has basically stabilized at more than 100, and there are more than 2,000 individual processing enterprises, with an annual processing of more than 20 million carats.
The second is jewelry processing. Jewelry processing in Changle County began at 1990, when there were only 1 processing enterprises and a few individual processing businesses. Jewelry processing is a family workshop, with poor conditions and backward technology. After 2000, Changle Jewelry has been upgraded by learning advanced technology. By 20 10, there are more than 2,000 jewelry processing and sales enterprises in the county, processing hundreds of millions of pieces of jewelry every year and digesting more than tons of precious metals (gold, platinum, palladium and silver) 100.
The third is the processing of jewelry and handicrafts. During the period of 1998, gem processing enterprises in this county began to embed sapphires in handicrafts and daily necessities, which expanded the jewelry sales market. The rise of sapphire inlay has promoted the development of high-grade handicrafts. For example, in 1997, five farmers in Sun, Wutu Street, carefully made a handicraft called "Baolong welcomes the return" with 1997 sapphire to celebrate the return of Hong Kong to the motherland. 1999, to commemorate the 50th anniversary of the founding of New China, they made the National Day Tower with sapphire. By 20 10, there will be more than 60 jewelry and handicraft processing enterprises in the county, processing more than 500 varieties of more than 20 types, with a number of millions.
5. Economic and technical evaluation of sapphire minerals
Sapphire is one of the four most precious gems in the world today. With the development of society, the value of gems in the world economic market is becoming more and more prominent. At present, the international sapphire market tends to be stable and there is a shortage of high-quality sapphire; However, with the improvement of people's living standards, the demand for sapphire is increasing gradually, so the development and application prospect of sapphire in China is bright.
(1) international resources and supply and demand situation
Gem industry is one of the fastest growing industries in the world, and it is a commodity in international trade. The price of precious stones and products increases by about 10% every year, which is higher than the price of general trade goods. From the variety of gemstones, sapphire accounts for about 6%. Generally speaking, the main producers of sapphire are Sri Lanka, Thailand, Myanmar and Australia. At present, the sapphire resources in Sri Lanka, Thailand and Myanmar tend to be exhausted, and the mining amount is not much. A considerable part of them rely on the past to acquire folk collections. Sri Lanka's supply has declined, but its quality has improved; Thailand's supply is small, and the price of high-quality sapphire rises rapidly; Australia, on the other hand, is rich in sapphire, and the exploitation amount is very large.
Sapphire belongs to the sapphire of Sri Lanka in quality, with pure blue, good transparency and the highest reputation; Thailand sapphire blue is also pure, transparent and deep, and has a long-standing reputation; Burmese sapphires are also better than those mentioned above, but most of them are light-colored and opaque, with figures and starlight. Most starlight gems in Thailand are black. Australian sapphires are mostly dark blue, and a few are blue, with good transparency, similar to Changle sapphire.
The demand and price of sapphire products in the international market are as follows:
Japan: There is a great demand for medium and high-grade sapphires of various sizes above $3,000/carat, and all kinds of sapphires with standard specifications less than 0.6g are not very popular. Taiwan Province Province: We need high-quality gemstones, and the price is above $5,000/carat. Hong kong: starlight sapphire is light gray-blue-black, with opacity greater than 0.4g wholesale price 150 ~ 300 USD/carat. Sapphire sales in the US market rank first in colored gems, with the price of 300 ~ 1500 USD/carat, high-quality mid-range sapphire 1000 ~ 5000 USD/carat, ordinary sapphire 100 ~ 500 USD/carat, and high-quality starlight sapphire1000.
In recent years, people tend to pursue high-quality sapphires with pure color and good transparency, while opaque sapphires are of low value. Only the large opaque sapphire with cat's eye or starlight is more valuable, but its price is still lower than that of the solid transparent sapphire with the same weight.
Hong Kong Shi Sheng International Art Auction Co., Ltd. announced on 20 12 that the price of sapphire rose 10 times in three years. It is understood that 60% of sapphires exported from China are sold at home, and the remaining 40% are mainly sold around the world through Thailand. With the weakness of European and American consumer markets, as a luxury consumer product, although the volume of sapphire has declined, the price has not declined.
The whole Asian gem market is characterized by rising prices and expanding markets. Through the investigation of the operators of China Gem City in Changle, the prices of major Asian sapphire exporting countries such as Myanmar, Thailand and Viet Nam are almost the same as those in China. Thailand's price above 4 carats is 600 ~ 2,500 yuan/carat, Sri Lanka's price is 6,000 yuan/carat, and the poor quality is1000 ~ 2,000 yuan/carat. The price of sapphire in Taiwan Province Province has reached 4000 USD/carat, and the highest price has reached 5500 USD/carat. The price of Japanese sapphire is roughly between $2,500 and $5,000 per carat.
(2) Domestic market conditions
With the rise of domestic gem industry, the improvement of people's economic living conditions and consumption power, and the increasing awareness of sapphire, sapphire is favored by more consumers. In recent years, the domestic sapphire market has developed rapidly, and the price and sales volume are also rising. The local sapphire price in Changle has increased from 50 ~ 60 yuan/carat in the 1990s to 600 ~ 1500 yuan/carat now, especially in the last decade (Table 2-7-2). It is believed that China will gradually become a major international sapphire consumer and exporter, and its price has gradually been in line with the international sapphire price.
Table 2-7-2 Changle Sapphire Price Questionnaire
(According to Changle Gem City 20 12)
6. Prospect analysis of Changle sapphire
Changle sapphire has good transparency, large particle size and few inclusions, but its color is dark, similar to that of Australian sapphire, but its particle size is larger than that of Australian sapphire. On the whole, it should occupy a place in the world jewelry industry like Australian sapphire (Australian sapphire ranks fourth after Sri Lanka, Thailand and Myanmar sapphires), but from the current situation, it is far from it. Some people in China regard Changle sapphire as dark. At the same time, the exported sapphires are sold at high prices abroad as Australian sapphires, especially the high-quality Changle sapphires are more expensive. The main reasons are as follows:
1) Changle sapphire mining area is difficult to control. There are many local idle laborers, and their quality is low. Despite the best efforts of the local government and the mine management department, it is difficult to fundamentally solve the problem, which leads to people's indiscriminate mining and rushing to sell sapphires, and sapphires flow abroad at extremely low prices.
2) Although there are many gem processing plants in China, most of them have rough processing quality, no uniform format and style, so it is difficult to wholesale in large quantities, with low credibility and unreasonable information. They don't understand the domestic and foreign markets, buy, process and sell blindly, or simply resell sapphire raw materials, becoming the second destroyer of sapphire resources in China.
3) Up to now, there is still no unified classification scheme for Changle sapphire in China. Most technicians engaged in sapphire know little about domestic sapphire, and even less about foreign sapphire. Sapphire is not graded in quality, and the price is uniform. When jewelers from Thailand, China, Hongkong and Taiwan Province come to Changle to buy, they collect high-quality and low-quality sapphires at a very low price, and then pick out the high-quality sapphires and sell them abroad at a high price, while the low-quality ones are sold to some domestic gem factories at a slightly lower price, thus earning a lot of profits. Australian gem experts believe that some good quality sapphires are considered bad at home and sold at low prices abroad, while some poor quality sapphires are considered good and cannot be sold at high prices at home. The end result is that high quality and low price are sold abroad, and then sold as Australian gems at high prices; Those with inferior quality are resold many times in China, or roughly processed, and it is difficult to sell them abroad, resulting in a backlog and falling prices. Time and again, it has accelerated the outflow of high-quality sapphires and a large backlog of inferior sapphires in China.
To sum up, there are several ways for Changle sapphire to find its own value and finally occupy a place in the international gem industry:
A. The state or collective concentrates idle labor to mine sapphire ore, and the price is uniformly managed by the state, and the outflow of raw materials is prohibited.
B establish a large gem processing factory with quality, reputation and information as its purpose, pay attention to personnel training, and sell semi-finished products and finished products abroad to earn foreign exchange.
C. Classify Changle sapphires uniformly, and pull the price of high-quality sapphires out of low-quality sapphires to prevent high-quality sapphires from flowing out at low prices.
D starlight sapphire, Changle starlight sapphire can be compared with Myanmar starlight sapphire. It has been found that there are blue, dark blue, brownish yellow, brown and dark brown. , large particles, beautiful star pattern, even 12 star pattern, the market is broad.
E. golden yellow and yellow sapphires. Small particles of golden yellow and yellow sapphire can often be seen in this area. Crystal clear after processing, very beautiful, very marketable.
F. According to the principle of "deeper and thinner", you can process products with lighter colors, or you can use sapphires with yellow stripes to process yellow on the bottom tips of faceted gems, which will also look light and beautiful.
G. As long as the style of dark blue sapphire is suitable, such as emerald, it is dignified and elegant for men to wear, and it also has a certain market abroad, especially in the United States.
H. artificial discoloration. At present, experts from many universities and scientific research units at home and abroad are devoted to the research of color-changing technology. If sapphire can be successfully changed, Changle sapphire will have a brand-new situation in the world.
Sapphire inlaid into finished jewelry, the value will increase exponentially, and the market will be wider, especially corundum below 2mm, which is inlaid into combined jewelry (group inlay), and the price is quite amazing. The comprehensively recovered corundum can be made into high-grade abrasives, and the corundum with higher strength is a high-quality refractory in the steel and ceramic industries. Therefore, the comprehensive utilization of corundum, improving the utilization rate of corundum and the output of gemstones will increase the resources of sapphire in this area, change the color of sapphire or study the cutting technology to make it beautiful, which will double the value of sapphire mines in this area.
7. Construction and development of Changle sapphire market
In recent years, the county government of Changle County has attached great importance to the development of jewelry industry, which is mainly composed of county sapphires, and issued a series of policies to promote the continuous development of jewelry industry in Changle County.
Hardware construction: Since 1989, Wutu Gemstone Street and Changle Gemstone Street have been established in Changle County, providing a trading platform for promoting the development of sapphire industry in Changle County. 1993, in order to standardize the whole sapphire market, China Gem City was established. China Gem City is located in the northeast of the county, including three functional areas: market trading area, comprehensive supporting area and gem processing area. With the development of sapphire industry in Changle county, the original gem city is far from meeting the market demand. The county party committee and government decided to build the International Jewelry Building, Liwei International Jewelry Plaza, Mingzhu Building, Yikela International Gem Capital, Shanghe International Gem City, etc. Up to now, the International Jewelry Building, Liwei International Jewelry Plaza, Mingzhu Building and Yikela International Gem Capital have been completed and put into use, providing a better platform for the jewelry industry in Changle County and greatly promoting Changle.
Software construction: In order to promote the development of sapphire industry, the county party committee and the county government formulated the Opinions on Further Accelerating the Development of Jewellery Industry in the County, and established Gemstone Association, Gemstone Appraisal Center and special management team, which further standardized the development of jewelry industry in Changle County.
Expanding publicity: In order to improve the popularity and brand effect of sapphire in Changle County, Changle County has successfully held 12 Jewelry Exhibition and 10 China (Changle) International Gem Festival since 196. China (Changle) International Gem Festival won the title of National Top 50 Festival. The transaction volume increased from $35.9 million in 1996 to $2.010/3.3 billion.
At present, there are more than 50,000 employees in the jewelry industry in Changle County, and there are more than 2,000 jewelry processing and sales enterprises, with an annual processing of tens of millions of carats of precious stones, hundreds of millions of ornaments and hundreds of tons of gold, and the annual transaction volume of 20 10 is 36 billion yuan. It is the largest jewelry distribution center in Jiangbei and the largest sapphire trading center in China. Among them, the most representative China Gem City is the only national large-scale jewelry wholesale market with the name of "China" approved by the State Administration for Industry and Commerce. It has gathered hundreds of jewelry products such as sapphire, diamond, gold, silver, jade, jadeite, crystal, pearl and agate, and has dozens of well-known trademarks and brands such as Blue Sky Jewelry, which has been rated as "Top 100 National Competitive Markets" and "Top 10 Chinese Jewelry and Art Markets" for many times. Changle County has also been awarded the titles of "China Jewelry and Jade Jewelry Characteristic Industry Base" and "China Jewelry Industry Base".
With the rapid development of national economy and the improvement of people's living standards, sapphire has increasingly become a fashionable product that people collect and wear, and its value has been recognized by people more and more. CCTV once reported the miracle of sapphire appreciation in Changle County with Crazy Stone. Changle County is located in the high-end industrial cluster area of Jiaodong Peninsula and the blue economic zone of Shandong Peninsula, with superior location and abundant resources, which provides strategic support for the better and faster development of Changle County. The sapphire-based jewelry industry in Changle County will have a greater development prospect and will promote the better and faster economic and social development in Changle County.
(2) Copper
Shangqing Copper Mine, located in the south of Shang Qing, is located at 1.5km south of Tanqiao Town and has been exploited on a large scale. There are three ore bodies with proven reserves of 4869 1t, which are small deposits. The copper mine has been closed 1978, but there are still 970t reserves.
(3) bentonite
Bentonite, also known as bentonite and bentonite, can be used to prepare drilling mud, as a binder for metallurgical pellets and foundry sand, as a thickener for lubricating grease, and as a filler for papermaking, rubber and other industries. The properties of bentonite mainly depend on the quality, dispersibility and content of montmorillonite. The bentonite in Changle County is slurry bentonite, which is mainly produced in Baodu Street in Xiaonan, Qijiazhuang in Wutu Street and Guandi. Bentonite in the two producing areas is grayish green, with no bedding and massive structure, with a reserve of 230.6 million t. In addition, bentonite is also produced in Honghe, Qiangqiang and Qiaoguan towns.
Wutu bentonite has been processed and exported to oil fields as mud raw materials.
(4) building sand
It is mainly distributed in Wenhe River Basin, Bailang River Basin and gaoya reservoir and Ma Song Reservoir Areas in Changle County.
The sand layers of Bailang River, Wenhe River and Honghe River are the main mining targets of building sand in this county. The development of sand layers in Bailang River, Wenhe River and Honghe River is related to the exposure of gneiss in the basin. According to the average excavation depth of 2m, the total sand content of Bailang River is about 4 million m3, that of Wenhe River is about180,000 m3, that of Honghe River is about 800,000 m3, and that of the whole county is about 24.05 million m3.
Construction sand is mainly dredged in gaoya reservoir and mined as a by-product.
At present, mining has been banned.
(5) Granite
The exposed granite that can be used as building stone in China is the biotite adamellite of Paleoproterozoic, which has gneiss-like structure. The mineral composition of rocks includes plagioclase, potash feldspar, quartz and biotite. The total amount of granite in the county is about 654.38+0 billion m3. Changle county is currently only mined in Jiangjuntang, Honghe Town. The mined granite can be used to produce washstone and terrazzo, and can also be used to repair subgrade, wall foundation, roads, bridges, ports and dams.
(vi) Basalt for building
Basalt is widely distributed in the county, mainly in Fangshan, Qiao Shan, Wohushan and other places. The ore bed is olivine basalt, and the main minerals are tholeiite-betonite, olivine and ordinary diabase. Basalt is mainly used as raw material for casting stone, producing rock wool, building and road building materials. Changle county has huge reserves, with a total reserve of 759 million tons. The mining areas in the county are mainly concentrated in Beiyan, which is used for processing road stones and as raw materials for processing rock wool.
At present, mining has been banned.
(7) K-feldspar and veined time
There are granite pegmatite veins and time-dependent pulse groups in potash feldspar, time-dependent granite pegmatite veins and time-dependent pulse types in the county, with a single pulse width of several meters and a length of several tens of meters, which belong to the time-dependent pulse for potash feldspar and ceramics. Yingjiu Town has developed a small amount of potash feldspar as a high-quality ceramic raw material, with a reserve of 530,000 tons, with a timely vein reserve of 1 10,000 tons.
(8) Granite gneiss (rock sand)
Mainly distributed in Yanqi-Zhu Han area, the reserve is about1000000 t, and the thickness varies from less than 1m to more than ten meters, which can replace river sand in construction projects.
(9) Brick clay
It's all over the county. The total amount of brick and clay in the county is 65.438+0.29 billion t, and the excavation points are scattered in five major river systems, 13 towns and 35 villages in the county, mostly on the platform near the riverbed below 100m above sea level. The exploitation of clay for brick and tile is mainly used in the production of brick and tile kiln. Since the country explicitly prohibited the use of cultivated clay to burn bricks, in 20 10, Changle county carried out the work of cleaning and rectifying brick kilns, closed all 64 brick kilns and 70 lime kilns in the county, illegally exploited and processed nearly 100 places, and dismantled production and processing equipment. At present, there are no brick kilns in the county. All the land has been reclaimed.
(10) mineral water
The basalt pore fissure water in the mineral water system in this county belongs to magnesium bicarbonate mineral water containing strontium and metasilicate. Mineral water is colorless, odorless, transparent, odorless and free of suspended matter. The water temperature is 16.5 ~ 17.5℃, and the contents of fluorine, cyanide, arsenic, mercury, cadmium, nickel, silver, nitrate and nitrogen meet the national standards. The contents of metasilicic acid and strontium beneficial to human body are high, and the contents of trace elements such as lithium and zinc are high.
(1 1) glass timely sandstone
The chemical composition of timely sandstone for glass in this county is silica, alumina, iron oxide, titanium dioxide and so on. The lower part is medium-grained timely sandstone, and the upper part is siltstone, shale and micrite limestone, with a thickness of more than ten meters to dozens of meters. The coal seam in Xiaozhaili Mine, Gaoya is generally anticline, with two wings bent. Xujiahe Mine has five layers, each layer is 1 ~ 2m thick, with shale and conglomerate. It is mainly used to manufacture flat glass and glassware, with a stock of 350,000 t, which was once mined on a small scale.