葡(pu)萄(tao)瑪瑙(nao)石石上通體滿(man)布色(se)彩斑讕、大小不一(yi)、渾然天成(cheng)的(de)珠狀瑪瑙(nao)小球,互相(xiang)堆(dui)積,流珠掛玉(yu),猶如串串葡(pu)萄(tao),故(gu)名。有(you)的(de)石上偶有(you)似魚眼睛(jing)一(yi)樣的(de)瑪瑙(nao)珠。
葡(pu)(pu)萄(tao)瑪(ma)(ma)瑙(nao)(nao)石(shi)(shi)(shi)多(duo)(duo)產于(yu)阿拉善(shan)的(de)(de)(de)(de)蘇宏圖(tu)以(yi)北20公里(li)處火山口附近,該火山北側戈壁灘中(zhong)(zhong)有瑪(ma)(ma)瑙(nao)(nao)、碧玉等高(gao)硅質奇石(shi)(shi)(shi),火山口附近的(de)(de)(de)(de)葡(pu)(pu)萄(tao)瑪(ma)(ma)瑙(nao)(nao)原礦脈多(duo)(duo)深藏于(yu)玄武(wu)巖(yan)(yan)的(de)(de)(de)(de)空隙中(zhong)(zhong)被(bei)白粉狀高(gao)領土所(suo)包裹,所(suo)產之石(shi)(shi)(shi)的(de)(de)(de)(de)形狀、顏(yan)色、珠粒大小基本(ben)相(xiang)象(xiang)。葡(pu)(pu)萄(tao)瑪(ma)(ma)瑙(nao)(nao)石(shi)(shi)(shi)多(duo)(duo)蘊存在(zai)火山噴發(fa)巖(yan)(yan)堆積物中(zhong)(zhong),從灘面(mian)上(shang)撿到的(de)(de)(de)(de)葡(pu)(pu)萄(tao)瑪(ma)(ma)瑙(nao)(nao)石(shi)(shi)(shi)珠大色純,玉透溫潤;從巖(yan)(yan)石(shi)(shi)(shi)中(zhong)(zhong)采掘而(er)來的(de)(de)(de)(de)則未經風(feng)沙磨礪,所(suo)以(yi)石(shi)(shi)(shi)膚不光滑,需油浸后方顯(xian)出(chu)艷(yan)麗肌膚。葡(pu)(pu)萄(tao)瑪(ma)(ma)瑙(nao)(nao)石(shi)(shi)(shi)是二(er)十世紀八十年(nian)代阿拉善(shan)石(shi)(shi)(shi)友發(fa)現(xian)(xian)的(de)(de)(de)(de)新石(shi)(shi)(shi)種,由于(yu)過多(duo)(duo)的(de)(de)(de)(de)開(kai)采,現(xian)(xian)已較難尋覓。
葡(pu)(pu)萄瑪(ma)瑙(nao)石(shi)的(de)(de)成(cheng)(cheng)(cheng)分主要是(shi)二氧化(hua)硅,形(xing)成(cheng)(cheng)(cheng)于火山口附近的(de)(de)大(da)型空(kong)洞(dong)(dong)(dong)中,硅膠熱液無法充滿整個空(kong)間,即(ji)以(yi)某一質點如砂粒、泥(ni)塊、水(shui)滴(di)凝聚成(cheng)(cheng)(cheng)珠(zhu)狀(zhuang)球狀(zhuang)或(huo)水(shui)滴(di)狀(zhuang),后來者附著于先(xian)期形(xing)成(cheng)(cheng)(cheng)的(de)(de)珠(zhu)體上,或(huo)懸于洞(dong)(dong)(dong)頂,或(huo)長(chang)(chang)于洞(dong)(dong)(dong)底,或(huo)掛于洞(dong)(dong)(dong)壁,越長(chang)(chang)越大(da),構成(cheng)(cheng)(cheng)串串葡(pu)(pu)萄狀(zhuang)。在此后漫長(chang)(chang)的(de)(de)歲月(yue)里,巖(yan)洞(dong)(dong)(dong)被粘土(tu)所充填,因此葡(pu)(pu)萄瑪(ma)瑙(nao)多埋于泥(ni)中,亦起到(dao)很好的(de)(de)保護(hu)作用。葡(pu)(pu)萄瑪(ma)瑙(nao)石(shi)是(shi)內蒙的(de)(de)獨特石(shi)種,由于形(xing)成(cheng)(cheng)(cheng)條件又十(shi)分苛刻,非(fei)常稀(xi)少。