dissenting.
The Court’s opinion may have a far-reaching effect on patentees of, and particularly successors in title to, the 33 million acres of land patented under the Stock-Raising Homestead Act of 1916 (SRHA). The Act provides, with respect to land patented, that the United States reserves title to “all the coal and other minerals.” 43 U. S. C. §299. At issue here is whether gravel is a mineral within the meaning of the Act. To decide this question, the Court adopts a new definition of the statutory term: “[T]he Act [includes] substances that are mineral in character (i. e., that are inorganic), that can be removed from the soil, that can be used for commercial purposes, and that there is no reason to suppose were intended to be included in the surface estate.” Ante, at 53.
*61This definition compounds, rather than clarifies, the ambiguity inherent in the term “minerals.”1 It raises more questions than it answers. Under the Court’s definition, it is arguable that all gravel falls within the mineral reservation. Ante, at 53-55, and n. 14, 59. This goes beyond the Government’s position that gravel deposits become reserved only when susceptible to commercial exploitation. See Tr. of Oral Arg. 18-20.2 And what about sand, clay, and peat?3 *62As I read the Court’s opinion it could leave Western homesteaders with the dubious assurance that only the dirt itself could not be claimed by the Government. It is not easy to believe that Congress intended this result.
h — <
In construing a congressional Act, the relevant intent of Congress is that existing at the time the statute was enacted. See Andrus v. Charlestone Stone Products Co., 436 U. S. 604, 611, and n. 8 (1978); Winona & St. Peter R. Co. v. Barney, 113 U. S. 618, 625 (1885). The Court avoids this rule of construction by largely ignoring the stated position of the Department of the Interior before 1916 that gravel— like sand and clay — was not a mineral.
In 1916, when the SRHA was enacted, the Department of the Interior’s rule for what it considered to be a “valuable mineral deposit” as those terms are used under the general mining laws4 was clear: “[WJhatever is recognized as a mineral by the standard authorities on the subject, whether of metallic or other substances, when the same is found in the public lands in quantity and quality sufficient to render the *63land more valuable on account thereof than for agricultural purposes, should be treated as coming within the purview of the mining laws.” Pacific Coast Marble Co. v. Northern Pacific R. Co., 25 L. D. 233, 244-245 (1897). See Letter from Commissioner Drummond to Surveyors-General, Registers, and Receivers (July 15, 1873) (reprinted in H. Copp, Mineral Lands 61, 62 (1881)). It is important to note that the Department’s test had two parts. First, before a substance would cause the Department to characterize land as mineral, it had to be recognized as a mineral by the standard authorities on the subject. See n. 1, supra. Second, the mineral had to appear in sufficient quantity and quality to be commercially exploitable.5
Under the Department of the Interior’s earliest decisions, certain commonplace substances were classified as minerals. See W. H. Hooper, 1 L. D. 560, 561 (1881) (gypsum); H. P. Bennet, Jr., 3 L. D. 116, 117 (1884) (permitting placer claims for building stone). But the Department soon began to recognize a small group of substances, that were valuable for certain purposes, as not being “minerals” “under all authorities.” In Dunluce Placer Mine, 6 L. D. 761, 762 (1888), the Secretary held that a deposit of “brick clay” would not warrant classification as a valuable mineral deposit. The Secretary so held despite a finding that the land on which the deposit was found was “undoubtedly more valuable as a ‘clay placer’ than for any other purpose.” Id., at 761.
The Department followed Dunluce in a number of subsequent cases.6 An important case under the general mining *64laws for our purposes is Zimmerman v. Brunson, 39 L. D. 310 (1910). It involved sand and gravel, and was decided four years before Congress began consideration of the SRHA. After quoting the rule in Pacific Coast Marble, the Secretary stated:
“A search of the standard American authorities has failed to disclose a single one which classifies a deposit such as claimed in this case as mineral, nor is the Department aware of any application to purchase such a deposit under the mining laws. This, taken into consideration with the further fact that deposits of sand and gravel occur with considerable frequency in the public domain, points rather to a general understanding that such deposits, unless they possess a peculiar property or characteristic giving them a special value, were not to be regarded as mineral.” 39 L. D., at 312.
The Secretary then reviewed the Department’s cases on clay and stone,7 concluding:
*65“From the above resume it follows that the Department, in the absence of specific legislation by Congress, will refuse to classify as mineral land containing a deposit of material not recognized by standard authorities as such, whose sole use is for general building purposes, and whose chief value is its proximity to a town or city, in contradistinction to numerous other like deposits of the same character in the public domain. Id., at 313.
The Secretary concluded that gravel was such a material, and this clearly remained the Department’s position until 1929.
The Zimmerman decision was recognized by Department officials in Litch v. Scott, 40 L. D. 467, 469 (1912), as foreclosing “the question as to the mineral character of the land,” even though “it [did] not appear that the [claimant’s] removal of the sand or gravel had any connection with the cultivation of the land and it was removed solely for the purpose of sale.” And in Hughes v. Florida, 42 L. D. 401 (1913), First Assistant Secretary Andreius A. Jones wrote: “The Department does not concur with the contention that this deposit [of shell rock] is a mineral within the meaning of the general mining laws. It presents features greatly similar to the deposits of sand and gravel considered in the case of Zimmerman v. Brunson. . . .” Id., at 403-404.
Thus, it was beyond question, when the SRHA was adopted in 1916, that the Department had ruled consistently that gravel was not a mineral under the general mining laws.8 The legislative history is silent on exactly how Con*66gress defined “mineral,” but it is equally clear that the Department participated actively in drafting the SRHA and in advising Congress.9 In light of this record, one must conclude that Congress intended the term “minerals” in the new statute to have the meaning so recently and consistently given it by the Department in construing and applying the general mining laws.10 As it was the agency authorized to *67implement the SRHA, its contemporaneous construction should be persuasive as to congressional intention. This Court previously had accorded this respect to the Department of the Interior. See, e. g., Burke v. Southern Pacific R. Co., 234 U. S. 669, 677-678 (1914); Northern Pacific R. Co. v. Soderberg, 188 U. S. 526, 534 (1903).
HH I — I
Despite the absence of “specific legislation by Congress,” the Department in Layman v. Ellis, 52 L. D. 714 (1929), which did not involve SRHA lands, overruled Zimmerman 13 years after the enactment of the SRHA.11 See 52 L. D., at *68721. As a result, individuals began staking mining claims on public land containing gravel deposits to obtain land patents, not for “mineral” value, but for such purposes as fishing camps and cabin sites. See H. R. Rep. No. 730, 84th Cong., 1st Sess., 5-6 (1955). Legislation in 1955 clarified the confusion that the Department’s decisions had created.12 Ulti*69mately, sand and gravel were once again removed from the coverage of the general mining laws;13 Congress reaffirmed the Zimmerman rule that common gravel is not a mineral under the general mining laws;14 and Layman was legislatively overruled.15
*70It is clear then that Congress never has, as the Court holds, considered all gravel to be a valuable mineral.16 And I see no basis for inferring congressional intent to classify gravel, contrary to all lay understanding, as mineral.17
*71I — I ( — I HH
Congressional interest m stockraising and mineral development was subordinate to the ultimate congressional purpose of settling the West. See H. R. Rep. No. 35, 64th Cong., 1st Sess., 14 (1916); H. R. Rep. No. 626, 63d Cong., 2d Sess., 10-11 (1914); n. 2, supra. More than cattle and more than minerals, it was the belief of Congress that
“the Nation as a unit needs more States like, for instance, Kansas and Iowa, where each citizen is the sovereign of a portion of the soil, the owner of his home and not tenant of some (perhaps) distant landlord, a builder of schools and churches, a voluntary payer of taxes for the support of his local government.” H. R. Rep. No. 626, supra, at 11 (emphasis added).
In recommending “citizen sovereignty” of the soil,18 Congress surely did not intend to destroy that sovereignty by reserv*72ing the commonplace substances that actually constitute much of that soil.19
The first attempt by the Department of the Interior to acquire ownership of gravel on SRHA lands did not occur until this case began in 1975. One would think it is now too late, after a half-century of inaction, for the Department to take action that raises serious questions as to the nature and extent of titles to lands granted under the SRHA.20 Owners of patented land are entitled to expect fairer treatment from their Government. In my view, the Department should be required to adhere to the clear intent of Congress at the time this legislation was adopted. I would affirm the judgment of the Court of Appeals.
To interpret the mineral reservation “to include substances that are mineral in character . . . and that there is no reason to suppose were intended to be included in the surface estate” is tautological, and to include all substances “that can be used for commercial purposes” is to ignore the prerequisites to commercial value of quantity and quality. The only factor that can be said to provide any guidance is that the substance must be one “that can be removed from the soil.” Moreover, the Department of the Interior has operated under a common definition of the statutory term “mineral” in the general mining laws for quite some time, and I therefore am puzzled why the Court creates a new one today. See 43 CFR § 3812.1 (1982) (“Whatever is recognized as a mineral by the standard authorities, whether metallic or other substance, when found in public lands in quantity and quality sufficient to render the lands valuable on account thereof, is treated as coming within the purview of the mining laws”); see n. 4, infra.
The Government’s claim is less inclusive because all parties agree that to hold that the homesteader has no right to use sand, gravel, and other common substances for his own purposes would pose a considerable impediment to the task of establishing a home and raising stock, undoubtedly the most important policies underlying the SRHA and the other Homestead Acts. See infra, at 71. The Court’s solution to the rancher’s problem is to allow the owner of the surface estate to use reserved minerals where such use is essential for stockraising and raising crops. See ante, at 54-55, n. 14. Thus, the Court apparently would give ranchers this free use of all reserved minerals, including “coal,” which is specifically mentioned in 43 U. S. C. § 299. I am not sure this Court should so lightly suggest such a broad exception to the mineral rights reserved by Congress. Moreover, such a free-use exception only invites litigation over what is a domestic use, who is a rancher, what is a ranch, what rights successors-in-interest have, and what rights a developer may have to halt such free use of “its” minerals.
My list is not exclusive. “Landowners have sold ‘moss rock,’ common rock on which moss has grown, to contractors to decorate fireplaces and *62homes. The rock has become ‘valuable/ but it is absurd to think that this common rock should now be included in a mineral reservation to the government.” Case Note, 18 Land & Water L. Rev. 201, 216 (1983).
By the phrase “general mining laws,” I refer primarily to the Mining Act of 1872, as amended, 30 U. S. C. § 21 et seq., which declares that “all valuable mineral deposits in lands belonging to the United States . . . shall be free and open to exploration and purchase . . . .” § 22. See generally ante, at 50-51. As the Court notes, ante, at 39, mineral exploitation of SRHA lands was made subject to the same restrictions that characterize development of lands under the general mining laws, and thus the interpretation of those laws is directly pertinent to determining congressional intent in 1916. It should be noted, however, that since 1955 it has been clear that a gravel deposit could not be “a valuable mineral deposit” under the general mining laws. See 30 U. S. C. § 611. The issue in this case is thus limited to the right of the Government to claim gravel found on SRHA lands, patented to private owners, even though the general mining laws still apply as to most minerals, but not to gravel.
Cf. 1 C. Lindley, American Law Relating to Mines and Mineral Lands § 98, pp. 174-175 (3d ed. 1914). The test whether a claimant has located a “valuable mineral deposit” under the general mining laws remains for the most part the same. See ante, at 44. As Justice Marshall concluded for a unanimous Court in Andrus v. Charlestons Stone Products Co., 436 U. S. 604, 610 (1978), mineral land must contain a deposit that both is a “mineral” and is “valuable.”
See, e. g., King v. Bradford, 31 L. D. 108, 109-111 (1901) (brick clay); Bettancourt v. Fitzgerald, 40 L. D. 620, 621-622 (1912) (clay useful for *64cement manufacturing); Holman v. Utah, 41 L. D. 314, 315 (1912) (clay and limestone); Victor Portland Cement Co. v. Southern Pacific R. Co., 43 L. D. 325, 326 (1914) (limestone shale); Mrs. A. T. Van Dolah, Solicitor’s Opinion A-26443 (Oct. 14,1952) (clay). See also Gray Trust Co., 47 L. D. 18, 20 (1919) (limestone useful in cement and road surfacing found not to qualify land as mineral land); Union Oil Co., 23 L. D. 222, 229 (1896) (petroleum) (overruled by Congress in Act of Feb. 11, 1897, ch. 216, 29 Stat. 526); Jordan v. Idaho Aluminum Min. & Mfg. Co., 20 L. D. 500, 501 (1895) (alumina) (but see Downey v. Rogers, 2 L. D. 707, 709 (1883) (permitting entry for alum); Tucker v. Florida R. & Navigation Co., 19 L. D. 414 (1894) (phosphate) (overruled in Pacific Coast Marble Co. v. Northern Pacific R. Co., 25 L. D. 233, 246-247 (1897)). Cf. Southwestern Mining Co., 14 L. D. 597, 602 (1892) (salt) (relying on consistent legislative policy to reserve saline lands from all land Acts).
Stone useful for building purposes was not classified as a mineral — at least for a time. See Conlin v. Kelly, 12 L. D. 1, 2-3 (1891) (declining to follow H. P. Bennet, Jr., 3 L. D. 116, 117 (1884)); Clark v. Ervin, 16 L. D. 122, 124 (1893); Hayden v. Jamison, 16 L. D. 537, 539 (1893); Florence D. Delaney, 17 L. D. 120, 121 (1893) (glass sand and building stone); Act of Aug. 4, 1892, 27 Stat. 348, 30 U. S. C. § 161 (making building *65stone a locatable mineral). Cf. Stanislaus Electric Power Co., 41 L. D. 655, 658-661 (1912) (§ 161 does not apply to common, low-grade rock having no special value for building purposes). The Department, however, later recognized claims founded on stone deposits that could be used for special purposes, such as monuments and ornamentation. See McGlenn v. Wienbroeer, 15 L. D. 370, 374 (1892).
In United States v. Aitken, 25 Philippine 7 (1913), the court held that commercial gravel was not a mineral. Relying on the Department’s administrative decisions, the court defined “mineral” as “ ‘[wjhatever is recognized as a mineral by the standard authorities on the subject.’ ” Id., at *6616 (quoting Letter from Commissioner Drummond to Surveyors-General, Registers, and Receivers (July 15, 1873)). The court found that if “an examination be made of the individual adjudicated cases and the decisions of the United States Land Department, upon which these general definitions of the term ‘mineral’ are based, it will be found that commercial gravel was not a factor in forming them, and that it has never been considered as a mineral.” Id., at 16. See D. Barringer & J. Adams, Law of Mines and Mining cxxv (1900) (list of 46 nonmetallic minerals that possess commercial value, but not listing gravel); D. Barringer, Minerals of Commercial Value (1897) (listing over 350 substances, including clay, petroleum, phosphate, salt, but not listing sand or gravel); 2 C. Lindley, supra n. 5, § 424, at 996-997 (recognizing Department’s policy for “commonplace substances such as ordinary clay, sand and gravel”); 1 W. Snyder, Mines and Mining § 144, p. 117 (1902) (discussing Department’s policy not to treat clay as a mineral).
In 1914, a bill to permit homesteading on unappropriated public lands in the West was referred by the House Committee on Public Lands to the Department of the Interior for comment. First Assistant Secretary Jones, six months after deciding Hughes v. Florida, 42 L. D. 401 (1913), submitted the Department’s report on the bill and at the same time submitted the Department’s draft of a substitute Stock-Raising Homestead Bill. After Committee hearings on the bills, Jones issued a second report to the Committee. See H. R. Rep. No. 626,63d Cong., 2d Sess., 1-9 (1914). The House passed the Department’s bill, but the full Senate failed to act on it. In the next Congress, the Department’s bill was reintroduced in the House. Again the Public Lands Committtee sought the advice of the Department. See H. R. Rep. No. 35, 64th Cong., 1st Sess., 4-8, 13 (1916). In the floor debates, Members made frequent reference to the fact that the Department had drafted the bill. See, e. g., 53 Cong. Rec. 1127 (1916) (statement of Congressman Taylor) (describing Department’s report as “one of the best reports we have ever had on any bill since I have been in Congress”); id., at 1130-1131.
The Court concludes that “[i]t is most unlikely that many Members of Congress were aware of the ruling in Zimmerman, which was never tested *67in the courts and was not mentioned in the Reports or debates on the SRHA.” Ante, at 46. The Court generally does not attribute such ignorance of the law to Congress. See, e. g., Lorillard v. Pons, 434 U. S. 575, 581 (1978); National Lead Co. v. United States, 252 U. S. 140, 147 (1920). And assuming ignorance seems especially inappropriate in this case, where during floor debates Congressmen referred to the Department’s administrative decisions and its interpretations of prior Homestead Acts. See 53 Cong. Rec. 1174 (1916). See also n. 9, supra.
Alternatively, the Court states that, “[e]ven if Congress had been aware of Zimmerman, there would be no reason to conclude that it approved of the Secretary’s ruling in that case rather than this Court’s opinion in [Northern Pacific R. Co. v.] Soderberg, [188 U. S. 526, 530 (1903)], which . . . quoted with approval a statement that gravel is a mineral.” Ante, at 46. I do not believe that the Soderberg Court’s one quotation from an English case is of greater relevance than the established views of the Department that is entrusted with the administration of the Federal Government’s public lands and that drafted the very Act before us now. Certainly the Soderberg Court did not think so, for in searching for a definition of the word “mineral,” it first examined “[t]he rulings of the Land Department, to which we are to look for the contemporaneous construction of these statutes.” 188 U. S., at 534. And the holding of Soderberg as to the classification of granite was not at all inconsistent with Department policy. See n. 7, supra.
Layman v. Ellis has been reaffirmed in subsequent opinions of the Department, but most of them provide the Court with none of the support it seeks in them. The Court also looks to two federal land-grant statutes that, like the SRHA, reserve all minerals to the United States. Ante, at 56-57. See United States v. Isbell Construction Co., 78 I. D. 385, 391, *68394-396 (1971); Dept. of Interior, Division of Public Lands, Solicitor’s Opinion, M-36379 (Oct. 3,1956). Relying on a prior opinion of the Department’s Solicitor, the Secretary in Isbell reversed the decision of the Director of the Bureau of Land Management holding that gravel was included in the patent. Moreover, the statute at issue in Isbell was passed after the Department’s decision in Layman, and differed in purpose and history from the SRHA. As the Department itself noted in this case, the statute there also differed from the SRHA as written in 1916 in that it originally provided from the date of its enactment for compensation for damages to the lands as well as to improvements. See 85 I. D. 129, 132, n. 2 (1978). The 1956 Solicitor’s Opinion simply relied on Layman. Interestingly, it took a much narrower view of what was included in the mineral reservation at issue there than the Court has with respect to the SRHA reservation: “[Deposits of sand and gravel in lands . . . patented under the act which can be shown as of the date of.. . patent to have a definite economic value by reason of the existence and nearness of a market in which they can be sold at a profit are reserved . . . .” Solicitor’s Opinion M-36379, supra, at 4 (emphasis added).
In a series of Acts culminating in the Surface Resources Act of 1955, 30 U. S. C. § 611, Congress removed such commonplace “materials” as gravel completely from the purview of the general mining laws. It is arguable, from this fact alone, that Congress never intended gravel to be a mineral under any of the mining laws. See United States v. Coleman, 390 U. S. 599, 604 (1968) (“ ‘[S]and, stone, [and] gravel... are really building materials, and are not the type of material contemplated to be handled under the mining laws . . .’”) (quoting 101 Cong. Rec. 8743 (1955)) (emphasis added by Court). Indeed, some officials in the Department initially concluded that under the Surface Resources Act “sand and gravel have been declared to be nonmineral substances and should therefore no longer be considered as being reserved to the United States under the mineral reservation in the [SRHA].” Dept. of Interior, Division of Public Lands, Solicitor’s Opinion, M-36417, p. 1 (Feb. 15,1957). Assuming, however, that the Department eventually may have concluded properly that the Act did not quitclaim common materials to SRHA patentees, see id., at 2, it is nevertheless difficult for the Department to contend that the Act is irrelevant *69to the inquiry whether the Government had title to the gravel in the first instance. Interestingly, the Act specifically permits continued location on public lands of gravel with “distinct and special value,” § 611, the same test set forth in Zimmerman for determining when a deposit of gravel would be considered a “valuable mineral deposit.” See United States v. Kaycee Bentonite Corp., 89 I. D. 262, 274 (1982) (1955 congressional test “echoes” Zimmerman test).
While the Department’s authority to dispose of gravel on “public lands” is clear, see n. 4, supra, it is not at all clear with respect to gravel on SRHA lands. The Court assumes without discussion agency jurisdiction to bring a trespass action on SRHA lands under regulations that authorize such actions for trespass on “public lands.” Yet there at least is doubt that SRHA lands are “public lands” as that term has been interpreted by this Court. See, e. g., Bardon v. Northern Pacific R. Co., 145 U. S. 535, 538 (1892); Mall, Federal Mineral Reservations, 20 Rocky Mt. Min. L. Inst. 399, 443-449 (1975). Furthermore, even if SRHA lands are public lands and gravel is reserved, the Department’s regulations apparently fail to permit disposal of minerals for these lands. See 30 U. S. C. § 601; 43 CFR § 3601.1 (1982) (stating that “mineral material disposals” may not be made from “public lands” on which there are “valid, existing claims to the land by reason of settlement, entry, or similar rights obtained under the public land laws”). Thus, the Court’s extended discussion of the policy of encouraging mineral development on SRHA lands has little relevance with respect to gravel and other commonplace substances. Indeed, if this case is any indication, it rather appears that the Government wants to prevent development of such materials.
The anomalous status of Layman and common varieties of gravel has not escaped the notice of the Department, which has commented that “the arguments advanced by the Department for overruling Zimmerman are difficult to distinguish from rationales that would support making common clay locatable.” Kaycee Bentonite, supra, at 274, n. 9.
See n. 12, supra. The Court relies on a dozen federal administrative and judicial cases since Layman but involving pre-1955 locations for the proposition that gravel deposits could be located under the general mining laws. See ante, at 57-58. But none of these cases involves SRHA land, they were concerned primarily with the application of the marketability *70test, and none questioned whether gravel was a mineral. The issue here, however, is whether gravel should ever be considered a “mineral” under the SRHA, and the cases are at the most evidence of how gravel should be treated on “public lands” under the mining laws after Layman and before Congress in 1955 removed all gravel from the purview of the mining laws. See n. 13, swpra. The only prior case addressing the precise issue before the Court held that ordinary sand and gravel were not reserved to the United States within the meaning of the mineral reservation contained in SRHA patents. See State ex rel. Highway Comm’n v. Trujillo, 82 N. M. 694, 487 P. 2d 122 (1971). Similar cases also suggest that gravel is not a reserved mineral. Cf. United States v. Union Oil Co. of California, 549 F. 2d 1271, 1279 (CA9) (SRHA reserved “unrelated subsurface resources”), cert. denied, 434 U. S. 930 (1977); Bumpus v. United States, 325 F. 2d 264 (CA10 1963) (finding a mineral reservation following condemnation not to include gravel).
Not even the Department has gone as far as the Court apparently would. Although Layman made common varieties of gravel locatable, gravel that “is principally valuable for use as fill, sub-base, ballast, riprap or barrow was never [a valuable mineral deposit],” despite the fact that it “might be marketable at a profit.” United States v. Verdugo & Miller, Inc., 371. B. L. A. 277, 279 (1978) (emphasis in original). See Tr. of Oral Arg. 50.
The Court relies heavily on the rule that land grants are construed favorably to the Government. See ante, at 59-60. The Court fails to note, however, that we recently made clear that, notwithstanding this rule, public grants are “ ‘not to be so construed as to defeat the intent of the legislature, or to withhold what is given either expressly or by necessary or fair implication.’” Leo Sheep Co. v. United States, 440 U. S. 668, 682-683 (1979) (quoting United States v. Denver & Rio Grande R. Co., 150 U. S. 1, 14 (1893)). See Burke v. Southern Pacific R. Co., 234 U. S. 669, 679 (1914) (Congress intended “mineral lands” to be applied “in their ordinary and popular sense”); id., at 676 (“doubtless the ordinary or popular signification of that term was intended”); Marvel v. Merritt, 116 U. S. 11, 12 (1885) (statutory terms “mineral. . . substances” have no “scientific meaning different from their popular meaning”). A good indicator of the “ordinary and popular sense” of a word is the common law’s use of it. The Court ignores this. See Reeves, The Meaning of the Word “Minerals,” 54 *71N. D. L. Rev. 419, 472 (1978) (“As a general rule . . . sand and gravel are usually held not to be a mineral in private grants or reservations of minerals”); id., at 431; Brief for United States in Bumpus v. United States, 325 F. 2d 264 (CA10 1973), pp. 7-14 (construing declaration of taking’s mineral reservation as not reserving gravel to former landowners).
Quite apart from the clear evidence of congressional intent at the time the SRHA was enacted in 1916, see Part I, supra, it is unreasonable to suppose that Congress ever intended — when it was enacting legislation to encourage settlement of the West — to reserve to the Federal Government the commonplace inorganic substances that actually constituted the soil of the patented land. The incentive to move to the West and settle on its semiarid land would have been diminished significantly if it had been understood that only limited rights in what most persons consider a part of the soil itself were being granted. Indeed, the legislative history is clear that, rather than intending to provide rights analogous to grazing leases upon the unappropriated public domain, Congress intended to promote permanent settlement. See 53 Cong. Rec. 1233-1234 (1916) (statement of Congressman Mondell) (“I wish [the Congressman] would not call the laws he refers to surface-entry laws, for they are not. They convey fee titles. They give the owner much more than the surface; they give him all except the body of the reserved mineral”).
Cf. H. R. Rep. No. 626, supra n. 9, at 3 (surface owners’ activities “can be carried on without being materially interfered with by the reservation of minerals and the prospecting for a removal of same from the land”). Based on similar concerns, the Department on occasion has limited the breadth of mineral reservations because of the obvious congressional intent. See Solicitor’s Opinion M-36379, supra n. 11, at 4.
The Department is in no position to adopt a new policy for land patents long granted. See Andrus v. Shell Oil Co., 446 U. S. 657 (1980). Its prior actions have caused the population generally, including respondent, to understand that gravel was not a reserved mineral. Cf. Western Nuclear, Inc. v. Andrus, 475 F. Supp. 654, 660 (Wyo. 1979) (“Until [1975], it was the practice of the Wyoming Highway Department, construction companies, and the ranchers owning the surface estate to treat the gravel as part of the surface estate, the gravel being sold or used by the rancher with the approval of the [Bureau of Land Management]”). As Justice Rehnquist stated for the Court in Leo Sheep Co., supra:
“Generations of land patents have issued without any express reservation of the right now claimed by the Government. Nor has a similar right been asserted before .... This Court has traditionally recognized the special need for certainty and predictability where land titles are concerned, and we are unwilling to upset settled expectations . . . .” 440 U. S., at 687 (footnotes omitted).