334 GEORGE F. KUNZ 



been discovered in California. This is not a new mineral 

 species, properly, but a compact massive variety of vesuvian- 

 ite (idocrase). It was first announced in the report of the 

 United States geological survey for 1901, by the writer, as 

 having been found by Dr. A. E. Heighway, on the south fork 

 of Indian creek, 12 miles from Happy Camp and 90 miles from 

 Yreka, in Siskiyou county, Cal. Here a hard and handsome 

 stone, varying in color from olive to almost grass green, and 

 taking a fine polish, outcrops for some 200 feet along a hill- 

 side about 100 feet above the creek, and large masses have 

 fallen into the bed of the creek. At first it was supposed to 

 be jade (nephrite), but upon analysis proved to be vesuvian- 

 ite. The fallen pieces were in some cases as much as 5 feet 

 square and 2 feet thick, of excellent quality for polishing, and 

 of varying shades of light to dark green. The associated rock 

 is precious serpentine. 



In the region about Lake Superior occur two or three pe- 

 culiar little minerals that have attained somie value as local 

 gem stones. These, in the order of their importance, are 

 chlorastrolite, thomsonite (properly mesolite), and lintonite; 

 besides one or two other varieties, rarer and of less account. 

 These are all nearly related in composition, being silicates of 

 alumina with varying amounts of lime and oxide of iron. 

 They are all found as rounded nodules, not from wear, how- 

 ever, but natural, as being the filling of small ovate cavities 

 (originally bubble holes) in the trap rocks of the region. As 

 the rocks decompose the harder nodules fall out, and are rolled 

 on the lake beaches or by streams,'"and are often supposed to 

 be pebbles, but they are not such in reality. They seldom 

 exceed half an inch in diameter, but when polished they make 

 quite pretty stones, and are in considerable demand for local 

 jewelry, as rings, studs, and the like. 



Prior to 1889 no precious opal had been found in the Unit- 

 ed States. At about that time, however, and during the sub- 

 sequent decade, several occurrences of it were discovered, and 

 mining operations were undertaken at some points with ap- 

 parent promise of successful yield. But for various reasons 

 no important or continuous production has been developed 

 as yet, although the igneous rocks of Washington, Idaho, 



